Estimating Genetic Diversity of Rice Landraces from Yunnan
中国大米的作文英语
中国大米的作文英语Rice is one of the most important staple foods in China and has been cultivated in the country for thousands of years. China is the world's largest producer and consumer of rice, accounting for nearly 30% of global rice production. The diversity of rice varieties grown in China is truly remarkable, with each region boasting its own unique strains adapted to the local climate and soil conditions.At the heart of China's rice production lies the fertile plains of the Yangtze River basin, which has long been the country's rice bowl. The region's warm, humid climate and abundant rainfall provide ideal conditions for rice cultivation. Farmers in this area have honed their rice-growing techniques over generations, passing down traditional methods that maximize yields while preserving the land's natural resources.One of the most famous rice varieties from the Yangtze region is Wuchang rice, named after the city of Wuchang in Hubei province. Wuchang rice is renowned for its delicate flavor, fluffy texture, and beautiful pearly-white grains. The rice is grown in the nutrient-richalluvial soils along the Yangtze River, which lend it a distinct sweetness and fragrance. Wuchang rice has been a staple of the Chinese diet for centuries and is highly prized for its exceptional quality.Further north, in the provinces of Heilongjiang and Jilin, farmers cultivate a different type of rice known as Heilongjiang rice or Northeastern rice. This hardy variety is able to withstand the region's cold, continental climate, with its long, harsh winters and short growing seasons. Heilongjiang rice is known for its firm texture, high starch content, and ability to retain its shape and flavor even after prolonged cooking. It is a staple food for many families in the Northeast and is also highly sought after for its nutritional value and versatility in cooking.Moving to the south, the lush, tropical climate of Guangdong and Guangxi provinces gives rise to another renowned rice variety –Xiaodongjiang rice. This medium-grain rice is renowned for its delicate aroma, soft and fluffy texture, and subtle sweetness. Xiaodongjiang rice is often used in traditional Cantonese cuisine, where it is steamed and served as a simple yet flavorful accompaniment to a variety of dishes.In the mountainous regions of Yunnan and Guizhou, farmers cultivate a unique type of rice known as Yunnan black rice orForbidden rice. This ancient grain is prized for its deep purple-black color, which is the result of high levels of anthocyanins, powerful antioxidants that give the rice its distinctive hue. Yunnan black rice has a nutty, slightly sweet flavor and a firm, chewy texture. It is not only a culinary delight but also highly nutritious, containing high amounts of fiber, vitamins, and minerals.Beyond the major rice-growing regions, China is home to numerous other rice varieties, each with its own unique characteristics. In the coastal provinces of Zhejiang and Jiangsu, farmers grow a delicate, fragrant rice called Dongting rice, named after the Dongting Lake region. In the northern province of Shandong, the famous Jiaozhou rice is prized for its plump, tender grains and mild, sweet flavor.The diversity of rice cultivated in China is not just a testament to the country's rich agricultural heritage but also a reflection of its geographical and climatic diversity. Each region's rice variety has been shaped by the local environment, traditional farming practices, and the culinary preferences of the local population.Preserving this rice diversity is of utmost importance, not only for maintaining China's food security but also for safeguarding the cultural and ecological heritage associated with rice cultivation. Many traditional rice varieties are under threat from the rapid modernization of agriculture, which has led to the widespreadadoption of high-yielding hybrid strains and the abandonment of traditional farming methods.In recent years, however, there has been a growing movement to protect and promote China's heritage rice varieties. Farmers, researchers, and food enthusiasts are working together to revive traditional rice cultivation techniques, promote the cultivation of heirloom rice strains, and educate the public about the cultural and nutritional value of these unique grains.One such initiative is the establishment of rice banks, which serve as repositories for the preservation of rare and endangered rice varieties. These banks not only safeguard the genetic diversity of rice but also provide farmers with access to a wider range of rice strains, allowing them to experiment with different cultivars and adapt to changing environmental conditions.In addition, many local governments and non-profit organizations have launched programs to support small-scale, sustainable rice farming practices. These initiatives provide training, technical assistance, and marketing support to help farmers maintain traditional rice cultivation methods and bring their high-quality, heritage rice products to the market.The efforts to preserve China's rice diversity are not just aboutsafeguarding a food crop – they are also about preserving the rich cultural heritage and ecological balance associated with rice cultivation. Rice has been deeply woven into the fabric of Chinese society, with its cultivation and consumption intertwined with the country's traditions, customs, and even spiritual beliefs.From the intricate rice paddy terraces of Yunnan to the lush, verdant rice fields of the Yangtze River basin, China's rice-growing landscapes are a testament to the ingenuity and resilience of its farmers. These landscapes not only produce the staple food that has nourished the Chinese people for millennia but also serve as vital habitats for a diverse array of flora and fauna, contributing to the overall ecological balance of the regions.As China continues to modernize and industrialize, it is crucial that the country's policymakers and agricultural stakeholders recognize the immense value of preserving the country's rice diversity. By supporting small-scale, sustainable rice farming, promoting the cultivation of heritage rice varieties, and educating the public about the cultural and nutritional significance of these grains, China can ensure that its rich rice heritage continues to thrive and nourish generations to come.。
Rice Plant Genome Genetic Diversity
Rice Plant Genome Genetic Diversity Rice is one of the most important staple crops in the world, providing food for billions of people. The rice plant genome is a complex structure that contains a vast amount of genetic diversity. This genetic diversity is essential for the survival of rice plants and for the development of new and improved rice varieties. In this essay, we will explore the importance of genetic diversity in the rice plant genome, its impact on rice production, and the challenges associated with maintaining and conserving this diversity.Genetic diversity is the variation in the genetic makeup of individuals within a species. In the case of the rice plant genome, genetic diversity is crucial for the plant's survival and adaptation to changing environmental conditions. The rice plant genome is highly diverse due to its long history of domestication and the natural selection process. The domestication of rice began over 10,000 years ago, and since then, rice has been cultivated in different regions of the world, resulting in the development of various rice varieties with unique genetic traits.The genetic diversity in the rice plant genome has a significant impact on rice production. Different rice varieties have varying levels of resistance to pests and diseases, tolerance to environmental stresses such as drought and flooding, and different grain qualities. For example, some rice varieties have a higher yield potential than others, while some have better grain quality for specific purposes such as making sushi or rice cakes. Therefore, the genetic diversity in the rice plant genome provides a valuable resource for developing new and improved rice varieties that can meet the diverse needs of consumers and farmers.However, the genetic diversity in the rice plant genome is under threat due to various factors such as climate change, land-use changes, and the intensification of rice production. These factors can lead to the loss of traditional rice varieties and the homogenization of rice production systems. The loss of genetic diversity in the rice plant genome can have severe consequences for rice production, as it reduces the plant's ability to adapt to changing environmental conditions and increases its susceptibility to pests and diseases.To maintain and conserve the genetic diversity in the rice plant genome, various conservation strategies have been developed. These strategies include in situ conservation, ex situ conservation, and the use of participatory plant breeding. In situ conservation involves the conservation of rice varieties in their natural habitat, while ex situ conservation involves the preservation of rice seeds in gene banks. Participatory plant breeding involves the involvement of farmers in the selection and breeding of new rice varieties, which helps to maintain the genetic diversity of rice plants and promotes the use of traditional knowledge in rice production.In conclusion, the genetic diversity in the rice plant genome is essential for the survival and adaptation of rice plants to changing environmental conditions. It also provides a valuable resource for developing new and improved rice varieties that can meet the diverse needs of consumers and farmers. However, the genetic diversity in the rice plant genome is under threat due to various factors, and it is essential to maintain and conserve this diversity to ensure the sustainability of rice production. Conservation strategies such as in situ conservation, ex situ conservation, and participatory plant breeding can help to maintain the genetic diversity of rice plants and promote the sustainable use of traditional knowledge in rice production.。
他研究了水稻 英语作文
他研究了水稻英语作文Title: Exploring the Wonders of Rice: A Journey into Rice Research。
Rice, the staple food for more than half of the world's population, has been the focus of extensive research for centuries. In recent years, scientists have delved deeper into understanding this versatile grain, uncovering its genetic diversity, nutritional benefits, and ecological significance. This essay explores the fascinating world of rice research, highlighting its importance and the strides made in unraveling its mysteries.Understanding Genetic Diversity:One of the key areas of research in rice revolves around its genetic diversity. Scientists have been studying various rice varieties to identify genes responsible for traits such as yield, disease resistance, and tolerance to environmental stresses. By exploring the genetic makeup ofdifferent rice strains, researchers aim to develop improved varieties that can address the challenges faced by farmers worldwide.Unraveling Nutritional Benefits:Beyond its role as a staple food, rice offers a wealth of nutritional benefits. Research has shown that rice is a good source of carbohydrates, providing essential energyfor the body. Moreover, certain varieties of rice, such as brown and wild rice, are rich in vitamins, minerals, and dietary fiber, contributing to overall health and well-being. Scientists continue to explore ways to enhance the nutritional profile of rice through breeding and genetic modification.Exploring Ecological Significance:Rice cultivation plays a significant role in shaping ecosystems and landscapes. Wetland rice paddies provide habitat for diverse flora and fauna, contributing to biodiversity conservation. Additionally, rice fields serveas important carbon sinks, helping mitigate climate change by sequestering carbon dioxide from the atmosphere. Understanding the ecological dynamics of rice cultivationis crucial for sustainable agricultural practices and environmental stewardship.Advancements in Technology:The field of rice research has witnessed remarkable advancements in technology, enabling scientists to study rice at the molecular level. Techniques such as genome sequencing, marker-assisted breeding, and CRISPR gene editing have revolutionized rice breeding programs, allowing for the development of tailored varieties with desired traits. Furthermore, remote sensing and precision agriculture techniques aid in optimizing rice cultivation practices, increasing efficiency, and reducing environmental impact.Challenges and Future Directions:Despite the progress made in rice research, significantchallenges lie ahead. Climate change, water scarcity, pests, and diseases pose threats to rice production globally. Addressing these challenges requires interdisciplinary collaboration, innovative approaches, and sustainable solutions. Furthermore, ensuring equitable access to improved rice varieties and technologies is essential for food security and poverty alleviation in rice-growing regions.Conclusion:In conclusion, rice research continues to be a dynamic and vital field, with implications for food security, nutrition, and environmental sustainability. Through advancements in genetics, nutrition, ecology, and technology, scientists are unraveling the complexities of rice and paving the way for a more resilient and productive future. By recognizing the importance of rice and investing in research and development, we can ensure the well-beingof current and future generations while safeguarding the planet's resources.。
Rice Plant Genomic Selection
Rice Plant Genomic SelectionRice is one of the most important crops worldwide, providing food for half of theworld's population. However, rice production is under threat from various factors, including climate change, pests, and diseases. To address these challenges, scientists have turned to genomic selection as a tool to improve rice breeding. Genomic selection involves using DNA markers to predict the performance of rice plants and select the best ones for breeding. In this essay, I will discuss the benefits and challenges of rice plant genomic selection from various perspectives.From a scientific perspective, rice plant genomic selection has several benefits. Firstly, it allows for the selection of plants with desirable traits such as high yield, disease resistance, and tolerance to environmental stresses. This is because genomic selection can identify the DNA markers associated with these traits and use them to predict the performance of rice plants. Secondly, genomic selection can speed up the breeding process by reducing the time and cost required to evaluate rice plants. Traditional breeding methods require several years of field trials to evaluate the performance of rice plants, but genomic selection can predict the performance of plants based on their DNA markers, reducing the time required for field trials. Finally, genomic selection can increase the genetic diversity of rice plants by identifying and selecting plants with unique DNA markers. This can lead to the development of new rice varieties that are better adapted to local conditions.From a farmer's perspective, rice plant genomic selection can improve crop yields and reduce losses due to pests and diseases. By selecting rice plants with desirable traits, farmers can increase their yields and reduce their dependence on pesticides and other chemicals. This can lead to higher profits and a more sustainable farming system. However, there are also challenges for farmers, such as the cost of purchasing new seeds and the need for specialized knowledge and equipment to implement genomic selection.From a societal perspective, rice plant genomic selection can contribute to food security by increasing crop yields and reducing losses due to pests and diseases. This is particularly important in developing countries where rice is a staple food and where food security is a major concern. Additionally, genomic selection can promote sustainableagriculture by reducing the use of pesticides and other chemicals, which can have negative impacts on the environment and human health. However, there are also concerns about the potential impact of genomic selection on small-scale farmers, who may not have access to the technology or the resources to implement it.From an ethical perspective, there are several concerns about the use of genomic selection in rice breeding. One concern is the potential for unintended consequences, such as the development of new pests or diseases that are resistant to the new rice varieties. This could have negative impacts on the environment and human health. Another concern is the potential for genetic discrimination, where certain groups of people may be excluded from access to the benefits of genomic selection, such as small-scale farmers or marginalized communities. Finally, there is a concern about the ownership and control of genetic resources, as the development of new rice varieties through genomic selection may lead to the privatization of genetic resources and the exclusion of certain groups from their use.In conclusion, rice plant genomic selection has the potential to improve rice breeding and contribute to food security and sustainable agriculture. However, there are also challenges and concerns that need to be addressed, such as the cost and accessibility of the technology, the potential for unintended consequences, and the ethical implications of its use. Therefore, it is important to approach rice plant genomic selection with caution and to ensure that it is used in a responsible and equitable manner.。
Evaluation of Genetic Diversity in Rice Subspecies Using Microsatellite Markers
Published March, 2002NI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES601 Hornes,A.Frijters,J.Pot,J.Peleman,M.Kuiper,and M.Zabeau.Xu,R.Q.,N.Tomooka,and D.A.Vaughan.2000.AFLP markers forcharacterizing the Azuki bean complex.Crop Sci.40:808–815.1995.AFLP:A new technique for DNA fingerprinting.NucleicAcids Res.23:4407–4414.Yeh,F.C.,R.C.Young,B.Timothy,T.B.J.Boyle,Z.H.Ye,and J.X.Mao.1997.POPGENE,the user-friendly shareware for population Wachira,F.N.,R.Waugh,C.A.Hackett,and W.Powell.1995.Detec-tion of genetic diversity in tea(Camellia sinensis)using RAPD genetics analysis.Molecular Biology and Biotechnology Center, markers.Genome38:201–210.University of Alberta,Canada.(http://www.ualberta.ca/ෂfyeh;veri-Wight,W.1962.Tea classification revised.Curr.Sci.31:298–299.fied September27,2001).Zhang,Q.,M.A.Saghai Maroof,T.Y.Lu,and B.Z.Shen.1992.Genetic Williams,J.G.K.,A.R.Kubelik,K.J.Livak,J.A.Rafalski,and S.V.Tingey.1990.DNA polymorphisms amplified by arbitrary primers diversity and differentiation of indica and japonica rice detected are useful as genetic markers.Nucleic Acids Res.18:6531–6535.by RFLP analysis.Theor.Appl.Genet.83:495–499.Evaluation of Genetic Diversity in Rice Subspecies Using Microsatellite MarkersJunjian Ni,Peter M.Colowit,and David J.Mackill*ABSTRACT molecular markers can reveal differences among acces-sions at the DNA level and thus provide a more direct, Molecular markers are useful tools for evaluating genetic diversityreliable,and efficient tool for germplasm conservation and determining cultivar identity.The purpose of this study was toevaluate the genetic diversity within a diverse collection of rice(Oryza and management.sativa L.)accessions,and to determine differences in the patterns of Several types of molecular markers are available for diversity within the two rice subspecies indica and japonica.Thirty-evaluating the extent of genetic variation in rice.These eight rice cultivars of particular interest to U.S.breeding programs include restriction fragment length polymorphism and two wild species accessions(O.rufipogon Griffithand O.nivara(RFLP)(Botstein et al.,1980),random amplified poly-Sharma et Shastry)were evaluated by means of111microsatellite morphic DNA(RAPD)(Welsh and McClelland,1990; markers distributed over the whole rice genome.A total of753alleles Williams et al.,1990),amplified fragment length poly-were detected,and the number of alleles per marker ranged from1morphism(AFLP)(Vos et al.,1995),and microsatellite to17,with an average of6.8.A positive correlation was found betweenor simple sequence repeat(SSR)(Tautz,1989).Of the number of alleles per locus and the maximum number of repeatsthese,RFLP and microsatellites are codominant mark-within a microsatellite pared to indica cultivars,thejaponica group showed significantly higher genetic diversity on chro-ers and their map positions on the rice genome are well mosomes6and7,and considerably lower diversity on chromosome known,while RAPD and AFLP markers involve the 2.All rice cultivars and lines could be uniquely distinguished,and use of random,largely dominant markers.Microsatel-the resulting groups corresponded exactly to the indica and japonica lites are PCR-based markers that are both technically subspecies,with japonica divided into temperate and tropical types.efficient and cost-effective to use and are available for With stepwise discrimination,two subsets of approximately30mark-rice(Chen et al.,1997;Temnykh et al.,2000).Compared ers were identified that produced genetic distance matrices and den-with RFLPs,microsatellite markers detect a signifi-drograms that were the same as those produced by means of allcantly higher degree of polymorphism in rice(Wu and 111markers.The results suggested that a relatively small number ofTanksley,1993;Yang et al.,1994),and are especially microsatellite markers could be used for the estimation of geneticsuitable for evaluating genetic diversity among closely diversity and the identification of rice cultivars.related rice cultivars(Akagi et al.,1997).The cultivated Asian rice species,O.sativa,is com-R ice has one of the largest ex situ germplasm collec-1988).Indica is the predominant tropical subspecies.posed of two subspecies,indica and japonica(Oka, tions in the world(Jackson and Juggan,1993).ThisThe japonica subspecies,consisting of temperate and accessible collection of diverse cultivated and wild ricetropical types,is widely grown in East Asia,North and germplasm has made great contributions to rice breed-South America,Australia,Mediterranean North Africa, ing.The development of isozyme and,later,DNAand Europe,and accounts for about20%of world rice marker technology has provided an efficient tool toproduction(Mackill,1995).The genetic diversity of ja-facilitate plant genetic resource conservation and man-ponica rice is thought to be lower than for indica rice agement.In rice,molecular markers have been used to(Glaszmann,1987;Zhang et al.,1992).The use of wide identify accessions(Olufowote et al.,1997;Virk et al.,crosses between different subspecies often results in 1995),to determine the genetic structure and patternsterility problems in the hybrids and their progenies, of diversity for cultivars of interest(Akagi et al.,1997;disruption of favorable linkage blocks and gene combi-Mackill,1995;Yang et al.,1994;Zhang et al.,1992),andnations,and linkage drag(Ikehashi and Araki,1986). to optimize the assembly of core collections(SchoenThe reduced recombination and distorted segregation and Brown,1995).Compared to morphological analysis,resulting from wide hybridization may cause difficultiesin selection for desired recombinants during the breed-J.Ni,Dep.of Agronomy&Range Science,Univ.of California,Davis,ing process(Pham and Bougerol,1993).From the view-CA95616-8515USA;P.M.Colowit,USDA-ARS,Dep.of Agron-point of rice breeders,it is preferable to identify and omy&Range Science,Univ.of California,Davis,CA95616-8515USA;and D.J.Mackill,International Rice Research Institute,DAPOAbbreviations:AFLP,amplified fragment length polymorphism; Box7777,Metro Manila,Philippines.Received3Nov.2000.*Corre-MAS,marker assisted selection;RAPD,random amplified polymor-sponding author(d.mackill@).phic DNA;RFLP,restriction fragment length polymorphism;simplesequence repeat,SSR.Published in Crop Sci.42:601–607(2002).602CROP SCIENCE,VOL.42,MARCH–APRIL2002Table1.List of rice accessions used to study microsatellite Table2.List of microsatellite markers used in the study.Marker marker variation.designations are from Chen et al.(1997)and Temnykh et al.(2000).Name Origin Subspecies–groupChromosome Microsatellite markerBlack Gora India IndicaIR40931Philippines Indica1RM5,RM9,RM81A,RM84,RM212,RM220,IR50R IRRI Indica RM237,RM238A,RM243,RM246,RM259,RM IR36IRRI Indica1,RM23,RM265,RM315,RM302Hunan Late Indica2China Indica2RM207,RM211,RM233A,RM240,RM250,RM262, N-22India Indica RM263,RM6,RM213,RM341,RM266GIZA178Africa Indica3RM232,RM251,RM130,RM22,RM135,RM156, GZ5121-5-2-1Africa Indica RM55,RM338,RM60GZ5470-14-1-2Africa Indica4RM261,RM241,RM142,RM127,RM177,RM317, Teqing China Indica RM348,RM307,RM185L-202USA-Ca Japonica-tropical5RM153,RM31,RM169,RM173,RM178,RM13,L-203USA-Ca Japonica-tropical RM291,RM274,RM334Labelle USA-So Japonica-tropical6RM30,RM3,RM204,RM253,RM136,RM170,87Y550USA-Ca Japonica-tropical RM340,RM345,RM193Lemont USA-So Japonica-tropical7RM82,RM234,RM214,RM172,RM51,RM10, Moroberekan Africa Japonica-tropical RM180Katy USA-So Japonica-tropical8RM152,RM137,RM52,RM126,RM223,RM230, Newbonnet USA-So Japonica-tropical RM337,RM264,RM256M-103USA-Ca Japonica-temperate9RM215,RM105,RM219,RM160,RM245,RM296, M-201USA-Ca Japonica-temperate RM278M-202USA-Ca Japonica-temperate10RM228,RM258,RM244,RM239,RM171,RM222, M-203USA-Ca Japonica-temperate RM271,RM311M-204USA-Ca Japonica-temperate11RM21,RM167,RM202,RM209,RM224,RM229, M-401USA-Ca Japonica-temperate RM254,RM332,RM287Italica Livorno Italy Japonica-temperate12RM247,RM235,RM155,RM20,RM17,RM313, WC1403Korea Japonica-temperate RM309,RM270Akitakomachi Japan Japonica-temperateKoshihikari Japan Japonica-temperateYukihikari Japan Japonica-temperate lite primer pairs were chosen to represent the entire rice ge-Arborio Italy Japonica-temperatenome at about15-to20-centimorgan intervals on the basis Calmochi102USA-CA Japonica-temperateCalrose USA-CA Japonica-temperate of the published rice microsatellite framework map(Temnykh Taipei309China Japonica-temperate et al.,2000)(Table2).The original sources and motifs for Uz Ros269Russia Japonica-temperate these markers can be found in Temnykh et al.(2000)and in Daegwanbyeo Korea Japonica-temperatethe RiceGenes database(/rice; S-201USA-CA Japonica-temperateHirayana Japan Japonica-temperate verified October2,2001).Polymerase chain reaction(PCR) GIZA176Africa Japonica-temperate analysis followed procedures recommended by the manufac-O.rufipogon Wild relative turer(ABI Prism377GeneScan Chemistry Guide,PE Biosys-O.nivara Wild relativetems,Foster City,CA)with minor modifications.It was per-formed in15L of a mixture containing50ng DNA,330n M use donors of important traits from within the sameof each primer,250M of each dNTP,and0.6U Taq DNApolymerase in reaction buffer[20m M TRIS pH8.0,50m M subspecies or cultivar group.For the application ofKCl, 1.5m M MgCl2,0.1mM EDTA,1mM DTT,50% marker assisted selection(MAS)within a subspecies,it(v/v)glycerol].Fluorescent d CTPs(330n M)labeled with is important to obtain information on the genetic diver-a rhodamine dye(R110,R6G)was incorporated into PCR sity within a rice subspecies over different genome re-products to enable detection of the fragments in the ABI377 gions.The excellent attributes of SSR markers and theautomated sequencing system(Perkin-Elmer).The PCR was availability of over300markers in rice(Temnykh et al.,run as follows:(i)an initial denaturation step of3min at94ЊC,2000)make it possible to obtain this information.(ii)35cycles of1min at94ЊC,2min at55ЊC,1.5min at72ЊC, Our objectives were to use microsatellite markers to and(iii)a final extension step for5min at72ЊC.For some evaluate the genetic variation within a diverse collection specific cDNA derived microsatellites,two different annealing of rice accessions,to determine differences in the pat-temperatures,61and67ЊC,were employed as described byTemnykh et al.(2000).PCR products were analyzed on a terns of diversity within two rice subspecies,to distin-sequencing gel(5%LongRanger,1ϫTBE buffer,6M urea)in guish different accessions,and to reveal the genetic rela-an automated ABI377sequencing apparatus(Perkin-Elmer). tionships among them.Fragment lengths were estimated using internal size standardsby GeneScan Analysis Software.MATERIALS AND METHODSAccessions used in the present study included10indica Data Analysiscultivars,eight tropical japonica cultivars,20temperate japon-The number of repeats for each allele was determined by ica cultivars,and O.rufipogon and O.nivara,two close rela-comparing the size of the PCR product with that of IR36 tives of O.sativa(Table1).Accessions were obtained from thewhose repeat number was characterized by Temnykh et al. Rice Germplasm Center at the International Rice Research(2000).Estimated repeat number was used in the following Institute(IRRI),Philippines,the Rice Experiment Station,analysis.The number of alleles per locus was based on an Biggs,CA,and the local collection at Davis,CA.evaluation of the38O.sativa cultivars and didn’t include thetwo wild species.The term polymorphism information content DNA Extraction and SSR Analysis(PIC)was originally introduced into human genetics byBotstein et al.(1980).It refers to the value of a marker for DNA extraction from rice leaves was as described in Re-don˜a and Mackill(1998).One hundred-eleven rice microsatel-detecting polymorphism within a population,depending onNI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES603Table 3.Mean values for allele number and PIC of different classes of microsatellite markers within rice and by subspecies.Both polymorphic and monomorphic microsatellites were included in the calculations.Class ofNumber Number of allelesPIC value microsatellite of markersmarkers O.sativa Indica Japonica O.sativa Indica Japonica Genomic libraries 877.41a† 4.62a 4.64a 0.650a 0.651a 0.501a cDNA-derived 24 4.50b 3.38b 2.88b 0.514b 0.456b 0.335b Poly (GA)n type 707.59a 4.66a 4.77a 0.657a 0.657a 0.512a Other 2-bp 7 6.57ab 4.43a 4.14ab 0.652ab 0.663ab 0.497a 3-bp 27 5.22b 3.81a 3.37b 0.546b 0.504b 0.375a 4-bp 2 3.50b 3.50a 1.50b 0.384b 0.500b 0.250a Complex 5 5.60ab 3.20a 3.20b 0.554a 0.460b 0.329a All1116.784.354.260.6210.6090.465†Means in a column followed by different letters are statistically different at P Ϯ0.05.the number of detectable alleles and the distribution of their 1982)and RFLPs (Wang and Tanksley,1989;Zhang frequency.In present study,PIC value of a marker was calcu-et al.,1992).As a measure of the informativeness of lated according to a simplified version after Anderson et al.microsatellites,the average PIC value was 0.62with the (1993):range of 0.10(RM60)to 0.91(RM204).The microsatellite markers derived from the genomic PIC i ϭ1Ϫ͚nj ϭ1P 2ijlibrary showed significantly higher genetic diversity than those derived from GenBank sequences (Table 3).Com-where P ij is the frequency of the j th allele for the i th marker,paring microsatellite markers with the different repeat and summed over n alleles.The PROC REG of SAS was motifs,those with GA repeats had the greatest number employed to study the relationship between the maximum of alleles and highest PIC values,while the 3-and 4-bp number of simple repeats and number of alleles or PIC value.motif markers had the lowest number of alleles and PIC Average number of alleles,average PIC value,and average values (Table 3).These results were consistent with genetic distance were computed on the basis of different rice those reported by Cho et al.(2000).subspecies,chromosomes and microsatellite classes,and the means were compared by the GLM (general linear models)There was a relationship between the number of al-procedure of SAS.The Tukey test was used to compare the leles detected at a locus and the maximum number of means of different classes.simple repeats within the targeted microsatellite DNA The presence (1)and absence (0)of alleles for each microsa-(r ϭ0.72,P Ͻ0.001).Thus,the larger the maximum tellite marker were recorded for all accessions and then con-repeat number in the microsatellite DNA,the larger verted to a genetic distance matrix.Genetic distances (Nei the number of alleles detected.A significant correlation and Li,1979)between two entries were computed asbetween PIC value and the maximum number of single GD ϭ1Ϫ[2N /(N i ϩN j )]repeats per microsatellite marker was also detected (r ϭ0.69,P Ͻ0.001).where N is the number of shared bands and N i and N j are the Most microsatellite primers amplified PCR products total number of bands for entries i and j .A cluster diagram in O.rufipogon (89%)and O.nivara (88%).In the case was constructed based on these distances by the UPGMA (average linkage)method using PROC CLUSTER of SAS of null alleles in these species,PCR amplifications were (SAS Institute Inc.,1989).The centroid,median and single repeated to exclude failed PCR reaction as the cause linkage clustering methods of PROC CLUSTER were also of the null allele.The null alleles can arise from point used to observe consistency of the clustering.Groups deter-mutation (s)in one or both of the primer sites.The low mined from the cluster analysis were used for canonical dis-percentage of null alleles in wild relatives of rice implied criminant analysis using the program PROC CANDISC of that most SSR primers developed for rice could be em-SAS.Squared Mahalanobis distances between class means ployed with O.rufipogon and O.nivara ,the close rela-were computed and the first two canonical variables were tive of O.sativa .For about one fifth of primers capable plotted for all accessions.The program PROC STEPDISC of of being amplified in wild relatives (20of 99in O.rufipo-SAS was used to choose the subsets of microsatellite markers that best represented the information in the total dataset.gon and 22of 98in O.nivara ),it was also noted that Pearson correlation coefficients (PROC REG of SAS)were the band sizes of PCR products of wild relatives were used to evaluate the relationship between genetic distances outside the range of those amplified from O.sativa ,calculated on the basis of sublets and the whole dataset.suggesting that those alleles identified in wild relatives might be unique and different from those detected in RESULTS AND DISCUSSION O.sativa .SSR Polymorphism in the Entire SampleComparison of Polymorphism between RiceThe 111SSR markers revealed 753alleles in the 38Subspecies and Chromosomescultivars.The number of alleles per locus varied widely Although there were fewer indica (10)than japonica among these markers,ranging from 1(RM238A and (28)cultivars included in the present study,the average RM193)to 17(RM204)with an average of 6.8.These number of alleles observed was similar in indica (4.4)to numbers are,on a per locus basis,much larger than that in japonica (4.3).The indica group had significantly those reported from previous studies using other types of markers such as isozymes (Glaszmann,1987;Second,greater average PIC value (0.609)than the japonica604CROP SCIENCE,VOL.42,MARCH–APRIL2002parison of genetic diversity within the indica and japonica groups based on microsatellite markers on different rice chromosomes.A)Average number of alleles.B)Average of PIC value.group(0.465)(Table3).The means of genetic distances tivars,and several studies have been performed to char-between cultivar pairs within the subspecies were alsoacterize the extent of genetic diversity and differentia-used to evaluate the genetic diversity of different sub-tion of these two rice groups(Oka,1988;Second,1982; species.The average genetic distance for the indicaYang et al.,1994;Zhang et al.,1992).Some marker group(0.675)was significantly greater than that for the alleles appeared to be diagnostic for rice subspecies. japonica group(0.484)(Fϭ140.0,PՅ0.001).TheFor eight markers(RM240,RM262,RM130,RM156, conclusion that indica rice has a higher level of genetic RM160,RM245,RM271and RM235),the indica culti-variation than japonica rice is in accordance with previ-vars had alleles that were not found in the japonica ous reports(Mackill,1995;Yang et al.,1994;Zhang et cultivars.For RM130and RM156on chromosome3, al.,1992).However,it should be noted that severalall the indica cultivars had the same allele,and it was closely related japonica cultivars were included.different from any allele found in the japonica cultivars. There has been extensive interest in characterizingFor RM240,RM262,and RM271,all the japonicas had the genetic differences between indica and japonica cul-the same allele,which was not be found in the indicaNI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES605Fig.2.Cluster diagram based on genetic distance calculated from111microsatellite marker alleles of38rice cultivars and two wild accessions. cultivars.In some cases,the allele sizes were sufficiently clude complications caused by different microsatellitetypes,one subset including87microsatellite markers different to suggest that these alleles could be assessedon agarose gels,which would make them attractive for derived from the genomic library and another subset easily identifying subspecies.including65genomic derived(GA)n microsatellite mark-To our knowledge,there is little information available ers were also used to calculate the means of number of for the difference in genetic diversity of rice subspeciesalleles and PIC value on different chromosomes for the for specific rice chromosomes.In the present study,the two pared with the results based on number of alleles and PIC value for markers on differentthe whole dataset,similar conclusions were drawn from chromosomes for indica and japonica groups were calcu-those two subsets(data not shown).lated to evaluate the genetic diversity.Both indica andThe information on genetic diversity of rice subspe-japonica groups showed a high level genetic variation cies for specific genomic regions will be quite useful forrice breeding programs.A major application of this on chromosome11(Fig.1).The number of alleles onthat chromosome was34%higher than the average work is to determine the feasibility of mapping genes based on all12chromosomes,and the average PICwithin the japonica subspecies,and in particular,within values were20%(indica)and30%(japonica)higher.the temperate japonica group,to which most California On the other hand,chromosomes5and8had relativelycultivars belong.Some traits such as cooking quality lower genetic diversity for both groups(Fig.1).How-cannot be accurately measured in wide crosses,wherethe grain quality requirements are completely divergent. ever,diversity of indica and japonica groups differedon chromosomes2,6,and7.For chromosomes6and The data reported here indicate that it should be possi-7,the indica group showed significantly lower geneticble to obtain adequate polymorphism in crosses be-diversity than the japonica group.In contrast,for chro-tween California cultivars and premium quality Japa-mosome2,genetic variation of indica rice was muchnese cultivars such as Koshihikari to map traits of interest. higher than that of the japonica group(Fig.1).To ex-For some traits controlled by the specific loci on chro-606CROP SCIENCE,VOL.42,MARCH–APRIL2002Table4.The two microsatellite marker subsets that fully charac-between tropical and temperate japonica types is not terize the rice accessions.firm(Glaszmann and Arraudeau,1986;Mackill,1995). Method Identified markers For indica subspecies,with the same standard(GDϽ0.56),10cultivars could be divided into six subclusters Forward RM130,RM334,RM173,RM170,RM84,RM256,RM241,RM212,RM13,RM237,RM23,RM258,(Fig.2).Considering the high level genetic diversityRM137,RM291,RM52,RM287,RM229,RM213,in the indica cultivars,GDϽ0.62was also used forRM169,RM222,RM60,RM1,RM51,RM127,subcluster analysis.In this case,the10indica accessions RM302,RM270,RM9,RM81A,RM232,RM207,RM271could be divided into three subgroups,corresponding to Backward RM5,RM9,RM81A,RM84,RM212RM220,RM237,Indian upland cultivars,Egyptian cultivars,and tropical RM243,RM246,RM259,RM1,RM23,RM265,RM315,RM302,RM207,RM211,RM233A,Asian lowland cultivars.On the whole,the clusteringRM240,RM250,RM262,RM263,RM6,RM213,results revealed by SSR closely reflected the previouslyRM341,RM266,RM232,RM251,RM130,RM22,understood relationship among these rice accessions.RM135,RM156,RM55,RM338,RM60,RM261,RM241The indica and the two japonica groups determinedfrom the cluster analysis were used to perform the ca-nonical discriminant analysis.The first two canonical mosome6and7,it will be easy for a breeder to transfer variables were plotted to observe the relationship of the the desirable trait using MAS by crossing within japon-three rice cultivar groups(data not shown).By means of ica subspecies.However,for the traits controlled by loci111microsatellite markers,each group could be clearly on chromosome2,it might be difficult to obtain markers distinguished from the others.The squared distances for use in marker-assisted breeding.Furthermore,the between the indica and japonica groups were536(tropi-differences in microsatellite diversity may reflect other cal)and534(temperate)compared to57between tropi-underlying genetic similarities,implying that one might cal and temperate japonica s.not find sources of new alleles for traits controlled by To identify an efficient subset of microsatellite mark-genes on this chromosome.Resistance to stem rot(Scle-ers,the dataset was subject to STEPDISC analysis.With rotium oryzae Cattaneo)in rice may be an example of forward and backward strategies,two subsets of micro-this.Resistance to this disease was not found among satellite markers,consisting of31and37markers,were japonica cultivars,and was introduced from an accession identified(Table4).Average allele numbers were6.7 of O.rufipogon.One of the important resistance loci and7.0for the forward and backward set compared was mapped on chromosome2(Ni et al.,2001).with6.8for the whole dataset.PIC values were0.58and0.65for the forward and backward set compared withClustering of Rice Cultivars0.62for the whole dataset.The31microsatellites identi-with Microsatellite Markers fied from FORWARD STEPDISC analysis were evenlydistributed on most of rice chromosomes with the ex-All38cultivated accessions and the two wild relativesception of chromosome11,while the37microsatellites could be easily distinguished even though some acces-from BACKWARD STEPDISC analysis were mainly sions were closely related.The UPGMA cluster diagramlocated on chromosomes1,2,3,and4.Both subsets showed two major clusters corresponding to the indicaincluded the microsatellites derived from the genomic and japonica subspecies,with additional sub-clusterslibrary and the GenBank sequences.Some markers di-within both indica and japonica clusters(Fig.2).Theagnostic for the rice subspecies,were involved in both same major groups and sub-clusters were observed bysubsets(RM130and RM271in the FORWARD subset, the centroid hierarchical,median hierarchical and singleRM130,RM240,RM262,and RM156in the BACK-linkage clustering methods.WARD subset).These two subsets of markers were With genetic distance(GD)Ͻ0.56as the standardused to calculate the genetic distances and cluster analy-for a subcluster,the japonica cluster could be dividedsis.All38cultivated accessions and two wild relatives into two groups.One group was the tropical japonicacould still be easily distinguished.A significant correla-cultivars that included three California long-grain culti-tion between the genetic distances calculated on the vars and four southern U.S.cultivars.The second clusterbasis of the total dataset and those based on the subsets contained temperate japonica cultivars and consistedwas found(for total/forward,rϭ0.983,PϽ0.001;for of two subgroups that remained together in differenttotal/backward,rϭ0.971,PϽ0.001).The cluster analy-clustering methods.One subgroup contained typicalses based on these two subsets corresponded exactly to California medium grain cultivars(M-103,M-201,M-202,that based on the whole dataset(data not shown).The M-203,M-401,M-204and Calrose).The other subgroupresults suggested that a relatively small number of mi-mainly contained temperate japonica cultivars fromcrosatellite markers could be employed to evaluate the East Asia(Akitakomachi,Koshihikari,Yukihikari,andgenetic diversity,to identify different accessions,and to Daegwanbyeo).The remaining temperate japonica ac-reveal the genetic relationship among them. cessions,however,could not be clustered with these twosubgroups.Morobereban,a tropical japonica cultivar,was placed in the temperate japonica group.This may REFERENCEShave occurred because Moroberekan was the only up-Akagi,H.,Y.Yokozeki,A.Inagaki,and T.Fujimura.1997.Highly land cultivar included;all other tropical japonica culti-polymorphic microsatellites of rice consist of AT repeats,and a vars were U.S.long-grain types.Another explanation classification of closely related cultivars with these microsatelliteis that previous studies have indicated that the boundaryloci.Theor.Appl.Genet.94:61–67.。
稻米饭粒延伸性的研究进展
符雨, 赵宏源, 肖梦楠, 等. 稻米饭粒延伸性的研究进展[J]. 华南农业大学学报, 2023, 44(5): 670-678.FU Yu, ZHAO Hongyuan, XIAO Mengnan, et al. Research progress on elongation of cooked rice[J]. Journal of South China Agricultural University, 2023,44(5): 670-678.特约综述稻米饭粒延伸性的研究进展符 雨 ，赵宏源，肖梦楠，张桂权，王少奎(广东省植物分子育种重点实验室/亚热带农业生物资源保护与利用国家重点实验室/岭南现代农业科学与技术广东省实验室/华南农业大学 农学院, 广东 广州 510642)摘要: 水稻饭粒延伸性是指米粒蒸煮时的延伸特性，用蒸煮后米粒长度增加值与蒸煮前米粒长度的比值来衡量，是评价稻米蒸煮食味品质的重要指标之一。
随着现代遗传学及基因组学相关理论和育种技术的发展，人们对水稻饭粒延伸性的遗传研究也日趋深入。
本文综述了影响水稻饭粒延伸性的相关因素及其遗传研究进展，指出了水稻饭粒延伸性遗传研究目前存在的主要问题，分析了水稻饭粒延伸性遗传研究的应用前景。
关键词: 水稻；饭粒延伸性；蒸煮食味品质；分子育种中图分类号: S511；S330.2；Q37 文献标志码: A 文章编号: 1001-411X(2023)05-0670-09Research progress on elongation of cooked riceFU Yu , ZHAO Hongyuan, XIAO Mengnan, ZHANG Guiquan, WANG Shaokui(Guangdong Provincial Key Laboratory of Plant Molecular Breeding/State Key Laboratory for Conservation and Utilization ofSubtropical Agro-Bioresources/Guangdong Laboratory for Lingnan Modern Agriculture/College of Agriculture,South China Agricultural University, Guangzhou 510642, China)Abstract: Cooked rice elongation (CRE) refers to the elongation characteristics of rice grains during cooking, is evaluated by the ratio of the added value of rice grain length after cooking to the length of rice grain before cooking. It is one of the important indicators of cooking and eating quality. With the development of modern genetics and genomics related theories and breeding technology, the genetic research of CRE has also become increasingly in-depth. In this paper, the related factors affecting CRE and the main progress of genetic research on CRE were summarized, the existing problems of genetic research on CRE were also pointed out, and the prospects of genetic research on CRE were analyzed.Key words: Oryza sativa L.; Cooked rice elongation; Cooking and eating quality; Molecular breeding水稻Oryza sativa L.是极为重要的粮食作物，世界上超过50%的人口以大米为主食[1]。
水稻非整倍体无性繁殖过程中的遗传稳定性
作物学报 ACTA AGRONOMICA SINICA 2011, 37(9): 1505−1510/zwxb/ISSN 0496-3490; CODEN TSHPA9E-mail: xbzw@本研究由国家自然科学基金项目(30170567, 30600345, 30770131, 30771210, 31070278)和江苏高校优势学科建设工程项目资助。
*通讯作者(Corresponding author): 于恒秀, E-mail: hxyu@, T el: 0514-********, Fax: 0514-********第一作者联系方式: E-mail: zygong@, Tel: 0514-********, Fax: 0514-********Received(收稿日期): 2011-01-12; Accepted(接受日期): 2011-05-20; Published online(网络出版日期): 2011-06-28. URL: /kcms/detail/11.1809.S.20110628.1012.024.htmlDOI: 10.3724/SP.J.1006.2011.01505水稻非整倍体无性繁殖过程中的遗传稳定性龚志云 石国新 刘秀秀 裔传灯 于恒秀*扬州大学江苏省作物遗传生理重点实验室 / 教育部植物功能基因组学重点实验室, 江苏扬州 225009摘 要: 无性繁殖是保存非整倍体的一个有效手段。
为研究该过程中非整倍体的遗传稳定性, 从水稻第8染色体短臂端三体(2n +·8S)自交后代中筛选出相应的端四体(2n +·8S+·8S), 其田间性状表现为植株矮小, 叶片非常窄且内卷, 结实率差。
在多年无性繁殖过程中, 该端四体所添加的其中1条·8S 容易丢失使无性系产生性状变异。
通过FISH 分析发现该无性变异系的原始株中所添加的2条·8S 具有以下特点: 其中1条·8S 在着丝粒区域检测不到水稻着丝粒的基本组分CentO 序列, 但可以检测到水稻着丝粒的另一基本组分CRR 序列, 该染色体可以稳定遗传; 另外1条·8S 在着丝粒区域同时检测不到CentO 和CRR 序列, 该染色体不能稳定遗传。
四级作文杂交水稻翻译英语
四级作文杂交水稻翻译英语Hybrid rice, also known as interspecific orintervarietal rice, is the result of crossing two different varieties of rice. This breeding technique has been widely used to improve rice yield, disease resistance, and adaptability to different environmental conditions.Hybrid rice has gained popularity in many countries due to its high yield potential. It has been reported that hybrid rice can increase yield by 15-20% compared to conventional rice varieties. This has led to its widespread adoption in rice-growing regions around the world.One of the key advantages of hybrid rice is its ability to resist diseases and pests. By combining the genetic traits of different rice varieties, hybrid rice plants are more resilient to common rice diseases and pests, reducing the need for chemical pesticides and herbicides.In addition to its high yield potential and diseaseresistance, hybrid rice also exhibits improved adaptability to different environmental conditions. This means that hybrid rice can be grown in a wider range of climates and soil types, making it a versatile option for rice farmers.Despite its many benefits, hybrid rice also has some drawbacks. One of the main challenges is the cost of hybrid rice seeds, which can be significantly higher than conventional rice seeds. This can be a barrier for small-scale rice farmers who may not have the financial resources to invest in hybrid rice seeds.Overall, hybrid rice has the potential to significantly improve rice production and food security around the world. With its high yield potential, disease resistance, and adaptability to different environmental conditions, hybrid rice is a promising option for rice farmers looking to increase their productivity and resilience.。
英语作文介绍杂交水稻
英语作文介绍杂交水稻Hybrid rice, also known as inter-specific or inter-subspecific hybrid rice, is a promising and innovative breeding technology that has revolutionized rice production worldwide. 杂交水稻，也称为种间或种下杂交水稻，是一项有前途的创新育种技术，已经在全球范围内彻底改变了水稻生产。
One of the key benefits of hybrid rice is its significantly improved yield potential. 由其非常显著的增产潜力是杂交水稻的主要优势之一。
Traditional varieties of rice often struggle to produce high yields due to inbreeding depression, which hinders the expression of the desired traits. 由于近交抑制的影响，传统水稻品种往往难以产生高产量，这一点大大地限制了理想特性的表达。
In contrast, hybrid rice demonstrates heterosis, or hybrid vigor, which results in increased yield potential and improved overall performance. 相比之下，杂交水稻呈现出杂种优势，也就是杂种活力，这导致了更高的产量潜力和整体表现的提高。
This has proven to be a game-changer in the world of agriculture, as it allows for greater food security and economic stability for rice-producing regions. 这已经被证明是农业世界中的一场革命，因为它为生产水稻的地区提供了更大的粮食安全和经济稳定。
Rice Plant Genome Quantitative Genetics
Rice Plant Genome Quantitative Genetics The rice plant genome is a complex system that plays a significant role in the production of rice, which is a staple food for millions of people around the world. Quantitative genetics is a field of study that aims to understand the genetic basis of complex traits, such as yield, disease resistance, and grain quality, in rice plants. This field of study has the potential to revolutionize rice production by identifying the genes responsible for these traits and developing new varieties of rice that are more productive, resilient, and nutritious.One of the main challenges in studying the rice plant genome is its sheer size and complexity. The rice genome is approximately 430 million base pairs long, which is more than twice the size of the human genome. This complexity makes it difficult to identify the specific genes that are responsible for specific traits, as there are many different genes that are involved in the same trait. However, recent advances in sequencing technology have made it possible to sequence the entire rice genome, which has opened up new avenues for research in this field.Another challenge in studying the rice plant genome is the fact that rice plants are highly variable. There are many different varieties of rice, each with its own unique set of traits. This variability makes it difficult to identify the specific genes that are responsible for specific traits, as different varieties may have different sets of genes that contribute to the same trait. However, this variability also presents an opportunity to identify new genes and traits that can be used to improve rice production.Despite these challenges, there have been many exciting advances in the field of rice plant genome quantitative genetics in recent years. For example, researchers have identified several genes that are responsible for important traits such as yield, disease resistance, and grain quality. By understanding the function of these genes, researchers can develop new varieties of rice that are more productive, resilient, and nutritious. In addition, researchers have developed new tools and techniques for analyzing the rice genome, such as genome-wide association studies and quantitative trait locus mapping, which have enabled them to identify new genes and traits that can be used to improve rice production.One of the most promising areas of research in rice plant genome quantitative genetics is the development of new varieties of rice that are more resilient to climate change. Climate change is expected to have a significant impact on rice production in the coming decades, as rising temperatures, changing rainfall patterns, and more frequent extreme weather events are likely to reduce yields and increase the incidence of pests and diseases. By identifying the genes that are responsible for resilience to these environmental stresses, researchers can develop new varieties of rice that are better able to withstand these challenges.Overall, the field of rice plant genome quantitative genetics is a rapidly evolving and exciting area of research. While there are many challenges to overcome, the potential benefits of this research are enormous, as it has the potential to revolutionize rice production and improve food security for millions of people around the world. As researchers continue to develop new tools and techniques for analyzing the rice genome, and as our understanding of the genetic basis of complex traits in rice plants continues to grow, we can expect to see many exciting new developments in this field in the coming years.。
描写中国杂交水稻的英文作文高中
描写中国杂交水稻的英文作文高中China has long been recognized as a global leader in agricultural innovation and technological advancements. One of the country's most significant achievements in this field is the development of hybrid rice, a remarkable innovation that has transformed the landscape of rice production worldwide. This essay will delve into the remarkable story of Chinese hybrid rice, exploring its history, the science behind it, and its profound impact on global food security.The origins of hybrid rice can be traced back to the 1970s, when a Chinese agronomist named Yuan Longping embarked on a groundbreaking journey to revolutionize rice cultivation. At the time, traditional rice varieties were struggling to keep up with the growing demand for food, particularly in China's rapidly expanding population. Yuan recognized the need for a more efficient and productive rice cultivar that could address this challenge.Through meticulous research and experimentation, Yuan and his team discovered the key to developing a successful hybrid rice variety. They identified the genetic mechanism of male sterility in riceplants, which allowed them to create a system where the female and male parents could be easily crossed to produce high-yielding hybrid offspring. This breakthrough paved the way for the development of the first commercially viable hybrid rice in 1976.The impact of this innovation was immediate and profound. Hybrid rice demonstrated a remarkable ability to outperform traditional rice varieties in terms of yield, with an average increase of 20-30% in production. This dramatic boost in productivity had a transformative effect on China's food security, enabling the country to meet the growing demand for rice and reduce its reliance on imports.The success of Chinese hybrid rice quickly captured the attention of the global agricultural community. Countries around the world began to adopt this technology, recognizing its potential to address the pressing challenge of food security. Today, hybrid rice is grown in more than 40 countries, including India, the Philippines, Vietnam, and the United States, among others.One of the key factors behind the widespread adoption of hybrid rice is its adaptability to diverse environmental conditions. The technology has been adapted to thrive in a wide range of climates, from tropical to temperate regions, and it has proven resilient to various biotic and abiotic stresses, such as pests, diseases, and environmental fluctuations.The science behind hybrid rice is both fascinating and complex. At its core, the technology relies on the genetic manipulation of rice plants to create a system of male sterility and fertility restoration. This process involves the identification and isolation of specific genes responsible for male sterility, which are then incorporated into the female parent line. The male parent line, on the other hand, carries the fertility restoration genes, allowing the hybrid offspring to produce viable and fertile seeds.The development of hybrid rice has also led to advancements in other areas of agricultural research and technology. For instance, the insights gained from the study of male sterility in rice have paved the way for the development of hybrid varieties in other important crops, such as maize, sorghum, and pearl millet. Additionally, the success of hybrid rice has spurred further research into the genetic and molecular mechanisms underlying crop productivity, opening up new avenues for crop improvement and optimization.Beyond its scientific and technological merits, the impact of hybrid rice on global food security cannot be overstated. By dramatically increasing rice production, the technology has played a crucial role in alleviating hunger and poverty in many parts of the world. In China alone, the adoption of hybrid rice has contributed to a significant reduction in the number of people living in poverty, with millions ofsmallholder farmers benefiting from the increased yields and improved livelihoods.The success of Chinese hybrid rice has also had broader implications for international cooperation and knowledge-sharing in the field of agricultural development. The technology has been widely disseminated through collaborative research projects, training programs, and technology transfer initiatives, enabling developing countries to harness the power of this innovation and adapt it to their local contexts.Looking to the future, the continued development and refinement of hybrid rice technology hold immense promise for addressing the global challenges of food security and sustainable agriculture. Researchers are exploring new avenues, such as the incorporation of climate-resilient traits, improved nutrient-use efficiency, and enhanced pest and disease resistance, to further enhance the productivity and adaptability of hybrid rice varieties.In conclusion, the story of Chinese hybrid rice is a testament to the transformative power of agricultural innovation and the critical role it plays in shaping a more food-secure and sustainable future for our planet. The remarkable achievements of Yuan Longping and his team have not only revolutionized rice production in China but have also had a profound impact on global food security, serving as a beaconof hope and inspiration for agricultural researchers and policymakers around the world.。
四级杂交水稻英语作文
四级杂交水稻英语作文Title: Advancements in Hybrid Rice Cultivation。
Hybrid rice, a groundbreaking innovation inagricultural science, has significantly transformed the landscape of rice cultivation worldwide. Developed through the crossbreeding of two genetically distinct varieties, hybrid rice offers a multitude of advantages overtraditional varieties, including higher yields, improved resistance to pests and diseases, and enhanced adaptability to various environmental conditions. In this essay, we will delve into the intricacies of hybrid rice cultivation and explore its implications for global food security.To begin with, the advent of hybrid rice has revolutionized agricultural practices by substantially increasing rice yields. Through the utilization of heterosis, or hybrid vigor, hybrid rice varieties consistently produce higher yields compared to their conventional counterparts. This heightened productivity notonly addresses the escalating demand for rice due to population growth but also alleviates pressure on arable land, thereby contributing to sustainable agricultural development.Moreover, hybrid rice exhibits enhanced resistance to pests and diseases, thereby reducing the reliance on chemical pesticides and promoting eco-friendly farming practices. By incorporating genetic traits for pest and disease resistance from the parent varieties, hybrid rice cultivars demonstrate greater resilience against common threats such as blast, bacterial blight, and stem borers. Consequently, farmers can minimize crop losses and increase their overall profitability while simultaneously safeguarding environmental and human health.Furthermore, hybrid rice demonstrates remarkable adaptability to diverse environmental conditions, including drought, salinity, and submergence. This adaptability is attributed to the genetic diversity inherited from the parent varieties, allowing hybrid rice plants to thrive in regions where traditional cultivars struggle to survive. Asa result, farmers are empowered to expand rice cultivation into previously inhospitable areas, thereby enhancing food security and livelihoods in vulnerable communities.In addition to its agronomic benefits, hybrid rice cultivation also fosters technological innovation and knowledge exchange within the agricultural sector. Researchers continually strive to develop new hybrid combinations with superior traits, utilizing cutting-edge biotechnological tools such as marker-assisted selection and genomic analysis. Furthermore, the dissemination of hybrid rice technologies through extension services and farmer training programs facilitates the transfer of knowledge and best practices, empowering farmers to optimize their yields and improve their standard of living.However, despite its numerous advantages, hybrid rice cultivation also presents certain challenges and limitations. One major concern is the high cost of hybrid seeds, which can be prohibitive for resource-constrained smallholder farmers. Additionally, the maintenance of genetic purity in hybrid seed production requiresmeticulous breeding and seed processing techniques to prevent contamination and ensure uniformity. Furthermore, the potential loss of genetic diversity in rice ecosystems due to the widespread adoption of a few high-yielding hybrid varieties underscores the importance of conservation efforts to preserve traditional landraces and wild relatives.In conclusion, hybrid rice cultivation represents a significant milestone in agricultural innovation, offering a sustainable solution to the pressing challenges of food security, environmental sustainability, and rural development. By harnessing the power of heterosis, hybrid rice varieties have revolutionized rice production worldwide, empowering farmers to achieve higher yields, mitigate pest and disease pressures, and adapt to changing climatic conditions. Moving forward, continued research and investment in hybrid rice technology are essential to unlock its full potential and ensure its equitable distribution to benefit farmers and consumers alike.。
英语作文介绍杂交水稻
英语作文介绍杂交水稻Hybrid rice, also known as crossbred rice, refers to rice varieties that are the result of crossing two different parent varieties. It has revolutionized rice production globally due to its high yield potential and adaptability to various environmental conditions. Here, we delve into the intricacies of hybrid rice.Origin and Development。
Hybrid rice development can be traced back to the late 1960s in China, pioneered by renowned scientist Yuan Longping. Yuan successfully bred the first high-yielding hybrid rice variety, known as IR8, which played a pivotal role in the Green Revolution. Since then, hybrid rice breeding has seen remarkable progress, with numerous improved varieties being developed and adopted worldwide.Advantages of Hybrid Rice。
1. High Yield: One of the most significant advantages of hybrid rice is its high yield potential. Compared to traditional rice varieties, hybrids can producesignificantly more grains per unit area, thereby increasing overall productivity.2. Better Disease Resistance: Many hybrid ricevarieties exhibit improved resistance to various diseases and pests, reducing the need for chemical pesticides and enhancing sustainability.3. Adaptability: Hybrid rice varieties are often more adaptable to different agro-climatic conditions, including drought, flooding, and salinity, making them suitable for cultivation in a wide range of environments.4. Uniformity: Hybrids tend to exhibit greater uniformity in terms of plant height, maturity, and grain quality, facilitating easier management and harvesting.Challenges and Considerations。
作文稻米十年之约例文
作文稻米十年之约例文英文回答：As a staple food in many cultures, rice holds great significance and plays a vital role in the lives ofmillions of people around the world. It is not just a source of sustenance but also a symbol of tradition, unity, and prosperity. The Ten-year Rice Pact, also known as "稻米十年之约" in Chinese, is a commitment made by individuals, communities, and nations to prioritize the cultivation, consumption, and preservation of rice for the next ten years.The Ten-year Rice Pact aims to address several challenges faced by rice production and consumption. Firstly, it seeks to promote sustainable farming practices that minimize the negative impact on the environment while maximizing yield. This involves adopting organic farming methods, reducing the use of pesticides and chemical fertilizers, and implementing efficient irrigation systems.By doing so, we can ensure the long-term viability of rice cultivation and protect the natural resources on which it depends.Secondly, the Ten-year Rice Pact encourages the preservation of traditional rice varieties and thepromotion of biodiversity. Many local rice varieties have been lost over the years due to the dominance of high-yield hybrid varieties. By preserving and cultivating traditional varieties, we can maintain the genetic diversity of riceand ensure the resilience of our food systems in the faceof climate change and other challenges.Furthermore, the Ten-year Rice Pact emphasizes the importance of fair trade and equitable distribution of rice. It seeks to eliminate exploitative practices in the rice industry and ensure that farmers receive a fair price for their produce. This can help reduce poverty and improve the livelihoods of rice farmers, especially in developing countries where rice farming is a major source of income.In addition to these goals, the Ten-year Rice Pact alsoaims to raise awareness about the nutritional value of rice and promote its consumption as part of a healthy diet. Rice is a rich source of carbohydrates, vitamins, and minerals, and its consumption can contribute to improved nutritionand food security. By educating people about the benefitsof rice and encouraging its inclusion in daily meals, wecan combat malnutrition and promote better health outcomes.中文回答：作为许多文化中的主食，稻米在全球数百万人的生活中具有重要意义并发挥着至关重要的作用。
高中英语作文袁隆平
高中英语作文袁隆平Yuan Longping, a name synonymous with agricultural innovation and food security, was a Chinese agronomist who dedicated his life to the development of hybrid rice. His work has had a profound impact on global food production, particularly in regions where hunger and malnutrition are prevalent.Born on September 1, 1930, in Beijing, Yuan Longping was a visionary who recognized the potential of genetic diversityin rice to increase yields. His research began in the 1960s, a time when China was grappling with food shortages. Determined to find a solution, Yuan embarked on a quest to create a strain of rice that could produce higher yields per acre.His breakthrough came in 1973 when he successfully developed the world's first hybrid rice variety. This new strain, which combined the genetic traits of two different rice varieties, was able to produce 20% more grain than traditional rice. This increase in yield was a game-changer for China, which was able to become self-sufficient in rice production within a decade.Yuan's work did not stop there. He continued to refine his hybrid rice varieties, and by the early 21st century, some strains were yielding as much as 50% more than the original hybrid rice. His research has not only helped to feed China's growing population but also contributed to global efforts tocombat hunger.Yuan Longping's legacy extends beyond his scientific achievements. He was a humble man who believed in sharing knowledge and technology for the betterment of humanity. He shared his hybrid rice technology with other countries, particularly in Asia and Africa, where it has helped to improve food security and reduce poverty.In recognition of his contributions to agriculture and food security, Yuan Longping received numerous awards and honors, including the World Food Prize in 2004 and the Mahathir Science Award in 2014. His work has been a beacon of hope for millions around the world, demonstrating the power of science and innovation to address some of humanity's most pressing challenges.Yuan Longping passed away on May 22, 2021, leaving behind a legacy that will continue to nourish and inspire for generations to come. His life serves as a reminder of the potential within each of us to make a difference and to work towards a world where no one goes hungry.In conclusion, Yuan Longping's dedication to the developmentof hybrid rice has not only transformed agriculture in China but also had a ripple effect across the globe. His life and work are a testament to the power of perseverance, innovation, and the pursuit of knowledge for the greater good. As we remember Yuan Longping, we are reminded of the importance of continued research and collaboration to ensure a food-secure future for all.。
杂交水稻四级英文作文
杂交水稻四级英文作文Hybrid Rice: A Breakthrough in Agricultural Innovation。
Introduction。
Hybrid rice, a remarkable achievement in the field of agricultural science, has revolutionized the way we approach food security and sustainability. This innovative technology has not only transformed the landscape of rice production but has also had a profound impact on globalfood supply and the lives of millions of people worldwide.The Development of Hybrid Rice。
The concept of hybrid rice was first introduced in the 1970s by Chinese scientist Yuan Longping, who is often referred to as the "Father of Hybrid Rice." His groundbreaking research and experiments paved the way forthe development of high-yielding hybrid rice varieties. By combining the genetic traits of two different rice lines,hybrid rice is able to exhibit heterosis, or hybrid vigor, resulting in significantly higher yields compared to traditional inbred rice varieties.The process of developing hybrid rice involves a complex and meticulous process of selecting and breeding the parental lines, ensuring the production of viable and robust hybrid seeds. This process requires a deep understanding of genetics, plant breeding, and agricultural practices, as well as a commitment to continuous research and innovation.The Benefits of Hybrid Rice。
杂交水稻好处的英语作文
杂交水稻好处的英语作文Title: The Advantages of Hybrid Rice。
Introduction:Hybrid rice, a crossbreed of two different rice varieties, has garnered significant attention inagricultural circles due to its numerous benefits. In this essay, we will explore the advantages of hybrid rice cultivation and its impact on agricultural productivity, food security, and environmental sustainability.Increased Yield:One of the primary advantages of hybrid rice is its ability to deliver higher yields compared to traditionalrice varieties. Through careful crossbreeding, hybrid rice exhibits enhanced genetic traits such as disease resistance, tolerance to environmental stressors, and improved grain quality. As a result, farmers can achieve greaterproductivity per unit of land, thereby addressing the growing demand for rice amid population growth and changing dietary preferences.Improved Disease Resistance:Hybrid rice varieties are often bred to possess heightened resistance to common diseases that afflict traditional rice crops. Diseases such as blast, bacterial blight, and sheath blight can devastate rice fields, leading to significant yield losses. By incorporating resistance genes from different parental lines, hybrid rice offers a proactive solution to mitigate the impact of these pathogens, reducing the reliance on chemical pesticides and promoting sustainable agriculture practices.Adaptability to Environmental Conditions:Climate change poses a significant challenge to global agriculture, affecting crop growth patterns and exacerbating yield variability. Hybrid rice demonstrates greater adaptability to diverse environmental conditions,including drought, flooding, and extreme temperatures. By harnessing the genetic diversity of parental lines, hybrid rice varieties exhibit resilience in the face of climatic uncertainties, ensuring more stable yields and safeguarding farmers' livelihoods against adverse weather events.Shorter Growth Duration:Another notable advantage of hybrid rice is its shorter growth duration compared to traditional rice varieties. Through selective breeding, hybrid rice cultivars are engineered to have accelerated growth cycles, allowing for more frequent planting and harvesting intervals. This characteristic not only maximizes land utilization but also enables farmers to respond more flexibly to market demands and seasonal fluctuations, enhancing their economic competitiveness and overall efficiency.Enhanced Nutritional Value:Hybrid rice varieties often boast improved nutritional profiles, offering higher levels of essential vitamins,minerals, and micronutrients compared to their conventional counterparts. By leveraging advancements in biotechnology and genetic engineering, researchers can tailor hybrid rice to address specific nutritional deficiencies prevalent in certain regions, thereby contributing to public health initiatives aimed at combating malnutrition and promoting dietary diversity.Environmental Sustainability:In addition to bolstering agricultural productivity, hybrid rice cultivation promotes environmentalsustainability through various mechanisms. By optimizing resource utilization and minimizing input requirements such as water, fertilizers, and pesticides, hybrid rice farming helps mitigate the ecological footprint associated with conventional agriculture. Furthermore, the adoption of hybrid rice can facilitate the conservation of biodiversity by preserving native genetic resources and reducing the spread of monoculture cropping systems.Conclusion:In conclusion, hybrid rice represents a promising innovation in modern agriculture, offering a host ofbenefits ranging from increased yields and disease resistance to environmental sustainability and nutritional enhancement. As global food security concerns intensify and agricultural systems grapple with mounting challenges, the widespread adoption of hybrid rice holds tremendouspotential to transform the way we cultivate and consumethis vital staple crop. By harnessing the power of genetic diversity and scientific ingenuity, hybrid rice stands as a beacon of hope in our quest for a more resilient, equitable, and sustainable food future.。
Rice Plant Genome Diversity
Rice Plant Genome DiversityRice is one of the most important crops in the world, feeding billions of people. The diversity of the rice plant genome is critical to maintaining the crop's resilience and adaptability to changing environmental conditions. However, this diversity is under threat due to various factors such as climate change, urbanization, and monoculture farming practices. In this response, I will explore the importance of rice plant genome diversity, the factors threatening it, and the measures that can be taken to conserve it.Rice plant genome diversity is important for several reasons. Firstly, it provides the raw materials for breeding new rice varieties with desirable traits such as disease resistance, high yield, and nutritional quality. Without genetic diversity, rice breeding programs would be limited, and the crop's ability to adapt to changing environmental conditions would be severely compromised. Secondly, genetic diversity is critical for the long-term survival of the crop. In the face of climate change and other environmental stresses, rice plants with diverse genomes are more likely to survive and thrive than those with limited genetic variation. Finally, genetic diversity is essential for preserving cultural and culinary diversity. Different rice varieties have unique flavors, textures, and cooking properties, and their conservation is important for maintaining traditional cuisines and food cultures.Despite the importance of rice plant genome diversity, it is under threat from various factors. One of the biggest threats is climate change. Rising temperatures, changes in rainfall patterns, and extreme weather events can all affect the growth and survival of rice plants. As a result, certain rice varieties may become extinct, reducing the overall genetic diversity of the crop. Another threat is urbanization. As cities expand, agricultural land is converted into buildings and infrastructure, reducing the area available for rice cultivation. This can lead to the loss of traditional rice varieties that are well adapted to local conditions. Finally, monoculture farming practices, where a single rice variety is grown over large areas, can also reduce genetic diversity. This is because the crop is vulnerable to pests and diseases, and the lack of genetic variation means that there are no resistant plants to act as a buffer.To conserve rice plant genome diversity, several measures can be taken. One approach is to collect and preserve seeds from different rice varieties in seed banks. Seed banks arerepositories of plant genetic material that can be used for breeding and research purposes. They provide a backup in case certain rice varieties become extinct or are no longer cultivated. Another approach is to promote traditional rice farming practices that encourage diversity. For example, in some parts of Asia, farmers grow several different rice varieties in the same field, creating a diverse ecosystem that supports beneficial insects and microorganisms. This approach can reduce the need for pesticides and fertilizers and improve soil health. Finally, breeding programs can be established to develop new rice varieties with desirable traits. These programs can use genetic diversity from existing rice varieties to create plants that are better adapted to changing environmental conditions.In conclusion, rice plant genome diversity is critical to maintaining the resilience and adaptability of the crop. However, it is under threat from various factors such as climate change, urbanization, and monoculture farming practices. To conserve this diversity, measures such as seed banking, traditional farming practices, and breeding programs can be taken. By preserving the genetic diversity of rice plants, we can ensure that the crop continues to provide food, cultural diversity, and economic benefits to billions of people around the world.。
Rice Plant Genome Gene Editing
Rice Plant Genome Gene EditingThe rice plant is one of the most important crops in the world, providing food for over half of the global population. However, rice production faces numerous challenges, including climate change, pest attacks, and diseases. To address these challenges, scientists are exploring ways to edit the rice plant genome to enhance its resilience and productivity. Gene editing is a powerful tool that allows scientists to modify the DNA of living organisms, including plants, to achieve desired traits. In this essay, we will explore the potential benefits and risks of rice plant genome gene editing.The potential benefits of rice plant genome gene editing are numerous. First, gene editing can help to increase the yield of rice plants by introducing traits that enhance their productivity. For example, scientists can edit the genes responsible for photosynthesis to improve the efficiency of converting sunlight into energy. This can result in higher yields of rice per acre, which is crucial for meeting the growing demand for food in the world. Second, gene editing can help to make rice plants more resilient to environmental stresses, such as drought, floods, and extreme temperatures. By introducing genes that enable rice plants to cope with these stresses, farmers can grow rice in areas that were previously unsuitable for cultivation. This can help to increase food security and reduce poverty in developing countries.However, there are also potential risks associated with rice plant genome gene editing. One of the main concerns is the unintended consequences of genetic modifications. Although scientists can target specific genes for editing, there is always a risk of off-target effects, where unintended genes are also modified. This can lead to unexpected outcomes, such as reduced yield, toxicity, or unintended effects on the ecosystem. Therefore, it is important to conduct thorough safety assessments and monitoring of gene-edited rice plants before they are released into the environment or consumed by humans.Another potential risk is the impact of gene-edited rice on biodiversity. Rice is a staple food for many species, including birds, insects, and mammals. Gene editing can alter the nutritional content and other traits of rice, which can affect the feeding habits and survival of these species. Moreover, gene-edited rice plants may crossbreed with wild rice plants,leading to unintended genetic modifications in the wild population. This can have unpredictable consequences for the ecosystem and biodiversity.In addition, there are ethical and social implications of rice plant genome gene editing. Some people argue that gene editing is a form of genetic engineering that goes against the natural order of life. They argue that humans should not play God by manipulating the genes of living organisms, as this can lead to unintended consequences and undermine the dignity and autonomy of life. Moreover, gene editing can exacerbate social inequalities by favoring large agribusinesses over small farmers, who may not have access to the technology or resources to adopt gene-edited crops. This can lead to further concentration of power and wealth in the hands of a few, exacerbating the already existing inequalities in the food system.In conclusion, rice plant genome gene editing has the potential to revolutionize rice production and enhance food security, but it also poses risks and challenges that need to be addressed. To ensure the safety and sustainability of gene-edited rice plants, it is crucial to conduct thorough safety assessments, monitor their impact on biodiversity, and engage in ethical and social debates about the role of gene editing in agriculture. Ultimately, the decision to adopt gene-edited rice plants should be based on a careful consideration of the benefits and risks, and a commitment to promoting the common good and protecting the dignity of life.。
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Ｒｅｃｅｉｖｅｄ ４ Ｆｅｂ． ２００４ Ａｃｃｅｐｔｅｄ ２５ Ｍａｙ ２００４Ｓｕｐｐｏｒｔｅｄ ｂｙ ｔｈｅ Ｎａｔｉｏｎａｌ Ｎａｔｕｒａｌ Ｓｃｉｅｎｃｅ Ｆｏｕｎｄａｔｉｏｎ ｏｆ Ｃｈｉｎａ （３０１２５０２９）， ｔｈｅ Ｎａｔｕｒａｌ Ｓｃｉｅｎｃｅ Ｆｏｕｎｄａｔｉｏｎ ｏｆ Ｙｕｎｎａｎ Ｐｒｏｖｉｎｃｅ， Ｃｈｉｎａ（２００２Ｃ００４１Ｍ）， Ｓｈａｎｇｈａｉ Ｃｏｍｍｉｓｓｉｏｎ ｏｆ Ｓｃｉｅｎｃｅ ａｎｄ Ｔｅｃｈｎｏｌｏｇｙ （０３ＤＪ１４０１４） ａｎｄ ｔｈｅ Ｈｉ－Ｔｅｃｈ Ｒｅｓｅａｒｃｈ ａｎｄ Ｄｅｖｅｌｏｐｍｅｎｔ （８６３） Ｐｒｏｇｒａｍｏｆ Ｃｈｉｎａ （ＡＡ２１１０９１）．＊ Ａｕｔｈｏｒ ｆｏｒ ｃｏｒｒｅｓｐｏｎｄｅｎｃｅ． Ｔｅｌ （Ｆａｘ）： ＋８６ （０）２１ ６５６４３６６８； Ｅ－ｍａｉｌ： ＜ｂｒｌｕ＠ｆｕｄａｎ．ｅｄｕ．ｃｎ＞．ｈｔｔｐ：／／ｗｗｗ．ｃｈｉｎｅｓｅｐｌａｎｔｓｃｉｅｎｃｅ．ｃｏｍＡｃｔａＢｏｔａｎｉｃａＳｉｎｉｃａ植 物 学 报 ２００４， ４６ （１２）： １４５８－１４６７Ｅｓｔｉｍａｔｉｎｇ Ｇｅｎｅｔｉｃ Ｄｉｖｅｒｓｉｔｙ ｏｆ Ｒｉｃｅ Ｌａｎｄｒａｃｅｓ ｆｒｏｍ Ｙｕｎｎａｎ ｂｙ ＳＳＲ Ａｓｓａｙａｎｄ Ｉｔｓ Ｉｍｐｌｉｃａｔｉｏｎ ｆｏｒ ＣｏｎｓｅｒｖａｔｉｏｎＺＨＵ Ｍｉｎｇ－Ｙｕ１， ２， ＷＡＮＧ Ｙｕｎ－Ｙｕｅ２， ＺＨＵ Ｙｏｕ－Ｙｏｎｇ２， ＬＵ Ｂａｏ－Ｒｏｎｇ１＊（１． Ｍｉｎｉｓｔｒｙ ｏｆ Ｅｄｕｃａｔｉｏｎ Ｋｅｙ Ｌａｂｏｒａｔｏｒｙ ｆｏｒ Ｂｉｏｄｉｖｅｒｓｉｔｙ ａｎｄ Ｅｃｏｌｏｇｉｃａｌ Ｅｎｇｉｎｅｅｒｉｎｇ， Ｉｎｓｔｉｔｕｔｅ ｏｆ Ｂｉｏｄｉｖｅｒｓｉｔｙ Ｓｃｉｅｎｃｅ，Ｆｕｄａｎ Ｕｎｉｖｅｒｓｉｔｙ， Ｓｈａｎｇｈａｉ ２００４３３， Ｃｈｉｎａ；２． Ｍｉｎｉｓｔｒｙ ｏｆ Ｅｄｕｃａｔｉｏｎ Ｋｅｙ Ｌａｂｏｒａｔｏｒｙ ｏｆ Ａｇｒｉｃｕｌｔｕｒｅ Ｂｉｏｄｉｖｅｒｓｉｔｙ ｆｏｒ Ｐｌａｎｔ Ｄｉｓｅａｓｅ Ｍａｎａｇｅｍｅｎｔ， Ｋｅｙ Ｌａｂｏｒａｔｏｒｙ ｏｆ ＰｌａｎｔＰａｔｈｏｌｏｇｙ， Ｙｕｎｎａｎ Ａｇｒｉｃｕｌｔｕｒａｌ Ｕｎｉｖｅｒｓｉｔｙ， Ｋｕｎｍｉｎｇ ６５０２０１， Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ： Ｅｉｇｈｔｙ－ｆｉｖｅ ｒｉｃｅ （Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．） ｖａｒｉｅｔｉｅｓ， ｉｎｃｌｕｄｉｎｇ ８２ ｒｉｃｅ ｌａｎｄｒａｃｅｓ ｃｏｌｌｅｃｔｅｄ ｆｒｏｍ １７ｖｉｌｌａｇｅｓ ｉｎ Ｙｕｎｎａｎ Ｐｒｏｖｉｎｃｅ ｏｆ Ｃｈｉｎａ ａｎｄ ｔｈｒｅｅ ｓｔａｎｄａｒｄ ｖａｒｉｅｔｉｅｓ ｒｅｐｒｅｓｅｎｔｉｎｇ ｔｙｐｉｃａｌ Ｉｎｄｉｃａ ａｎｄ Ｊａｐｏｎｉｃａｅｃｏｔｙｐｅｓ， ｗｅｒｅ ｓｔｕｄｉｅｄ ｕｓｉｎｇ ｓｉｍｐｌｅ ｓｅｑｕｅｎｃｅ ｒｅｐｅａｔ （ＳＳＲ） ｍａｒｋｅｒｓ ｔｏ ｅｓｔｉｍａｔｅ ｔｈｅｉｒ ｇｅｎｅｔｉｃ ｄｉｖｅｒｓｉｔｙ ｆｏｒｔｈｅ ｐｕｒｐｏｓｅ ｏｆ ｓｔｒａｔｅｇｉｃ ｃｏｎｓｅｒｖａｔｉｏｎ． Ｎｉｎｅｔｅｅｎ ｓｅｌｅｃｔｅｄ ＳＳＲ ｐｒｉｍｅｒ ｐａｉｒｓ ａｍｐｌｉｆｉｅｄ ａ ｔｏｔａｌ ｏｆ ８３ ＳＳＲａｌｌｅｌｅｓ， ｗｉｔｈ ｍｏｌｅｃｕｌａｒ ｗｅｉｇｈｔ ｒａｎｇｉｎｇ ｆｒｏｍ １００ ｔｏ ５００ ｂｐ， ｆｒｏｍ ｔｈｅ ８５ ｒｉｃｅ ｖａｒｉｅｔｉｅｓ． Ａｎ ＵＰＧＭＡ ｄｅｎｄｒｏ－ｇｒａｍ ｂａｓｅｄ ｏｎ ｔｈｅ ｃｌｕｓｔｅｒ ａｎａｌｙｓｉｓ ｏｆ ｇｅｎｅｔｉｃ ｓｉｍｉｌａｒｉｔｙ ｏｆ ｔｈｅ ＳＳＲ ａｌｌｅｌｅｓ ｓｈｏｗｅｄ ａ ｓｉｇｎｉｆｉｃａｎｔ ｇｅｎｅｔｉｃｖａｒｉａｔｉｏｎ ａｍｏｎｇ ｔｈｅ ｉｎｃｌｕｄｅｄ ｒｉｃｅ ｖａｒｉｅｔｉｅｓ， ｗｉｔｈ ｔｈｅ ｓｉｍｉｌａｒｉｔｙ ｃｏｅｆｆｉｃｉｅｎｔｓ ｖａｒｙｉｎｇ ｂｅｔｗｅｅｎ ０．１５２ ａｎｄ０．９００． Ｈｏｗｅｖｅｒ， ｇｅｎｅｔｉｃ ｄｉｖｅｒｓｉｔｙ ｏｆ ｔｈｅ ｒｉｃｅ ｖａｒｉｅｔｉｅｓ ｃｏｌｌｅｃｔｅｄ ｆｒｏｍ Ｙｕｎｎａｎ ｗａｓ ｕｎｅｖｅｎｌｙ ｄｉｓｔｒｉｂｕｔｅｄｏｖｅｒ ｔｈｅｉｒ ｇｅｏｇｒａｐｈｉｃａｌ ｌｏｃａｔｉｏｎｓ． Ｔｗｏ ｄｉｓｔｉｎｃｔ ｇｒｏｕｐｓ ｗｅｒｅ ｉｄｅｎｔｉｆｉｅｄ ｆｒｏｍ ｔｈｅ ｃｌｕｓｔｅｒ ａｎａｌｙｓｉｓ ｏｆ ｔｈｅ ８５ｒｉｃｅ ｖａｒｉｅｔｉｅｓ ａｔ ｔｈｅ ｓｉｍｉｌａｒｉｔｙ ｃｏｅｆｆｉｃｉｅｎｔ ｌｅｖｅｌ ｏｆ ０．１５２， ｗｉｔｈ ｏｎｅ ｇｒｏｕｐ ｔｈａｔ ｉｎｃｌｕｄｅｄ ａｌｍｏｓｔ ａｌｌ ａｃｃｅｓｓｉｏｎｓｏｆ Ｉｎｄｉｃａ ｅｃｏｔｙｐｅ ａｎｄ ａｎｏｔｈｅｒ ｇｒｏｕｐ ｔｈａｔ ｃｏｎｔａｉｎｅｄ ａｌｌ ａｃｃｅｓｓｉｏｎｓ ｏｆ Ｊａｐｏｎｉｃａ ｅｃｏｔｙｐｅ． Ｖａｒｉｅｔｉｅｓ ｔｈａｔｓｈａｒｅｄ ｔｈｅ ｓａｍｅ ｎａｍｅｓ ｂｕｔ ｃｏｌｌｅｃｔｅｄ ｆｒｏｍ ｄｉｆｆｅｒｅｎｔ ｖｉｌｌａｇｅｓ ｄｉｄ ｎｏｔ ａｌｗａｙｓ ｓｈｏｗ ａ ｃｌｏｓｅ ｇｅｎｅｔｉｃ ｒｅｌａｔｉｏｎｓｈｉｐ，ｉｎｄｉｃａｔｉｎｇ ｍｉｓｉｄｅｎｔｉｆｉｃａｔｉｏｎ ｏｆ ｓｏｍｅ ｖａｒｉｅｔｉｅｓ ｂｙ ｌｏｃａｌ ｆａｒｍｅｒｓ． Ｉｔ ｉｓ ｃｏｎｃｌｕｄｅｄ ｆｒｏｍ ｔｈｉｓ ｓｔｕｄｙ ｔｈａｔ ｃｏｎｓｅｒ－ｖａｔｉｏｎ ｏｆ ｇｅｎｅｔｉｃ ｄｉｖｅｒｓｉｔｙ ｉｎ ｒｉｃｅ ｌａｎｄｒａｃｅｓ ｉｓ ｕｒｇｅｎｔｌｙ ｎｅｃｅｓｓａｒｙ ｉｎ Ｙｕｎｎａｎ， ｇｉｖｅｎ ｔｈｅｉｒ ｈｉｇｈ ｌｅｖｅｌ ｏｆｄｉｖｅｒｓｉｔｙ， ｂｕｔ ａｎ ａｐｐｒｏｐｒｉａｔｅ ｓｔｒａｔｅｇｙ ｎｅｅｄｓ ｔｏ ｂｅ ｆｏｌｌｏｗｅｄ ｔｏ ｇｕａｒａｎｔｅｅ ｔｈｅ ｅｆｆｅｃｔｉｖｅｎｅｓｓ ｏｆ ｃｏｎｓｅｒｖａｔｉｏｎａｃｔｉｖｉｔｉｅｓ． Ｐｒｏｐｅｒｌｙ ｓｅｌｅｃｔｅｄ ＳＳＲ ｐｒｉｍｅｒ ｐａｉｒｓ ｍｉｇｈｔ ｐｒｏｖｉｄｅ ａｎ ｉｄｅａｌ ｍｅｔｈｏｄ ｆｏｒ ｉｄｅｎｔｉｆｙｉｎｇ Ｉｎｄｉｃａ ａｎｄＪａｐｏｎｉｃａ ｅｃｏｔｙｐｅｓ ｆｏｒ ｒｉｃｅ ｃｏｎｓｅｒｖａｔｉｏｎ ａｎｄ ｂｒｅｅｄｉｎｇ ｐｒｏｇｒａｍｓ．Ｋｅｙ ｗｏｒｄｓ： Ｏｒｙｚａ ｓａｔｉｖａ； ｒｉｃｅ ｌａｎｄｒａｃｅ； ｄｉｆｆｅｒｅｎｔｉａｔｉｏｎ； ＳＳＲ； ｃｏｎｓｅｒｖａｔｉｏｎ； ｍｏｌｅｃｕｌａｒ ｍａｒｋｅｒChina is the world largest rice (Oryza s ativa )-producing and -consuming country, where rice culture also plays an important role in indigenous beliefs and practices in many agricultural regions. As a part of the origin and diversifica-tion center for Asian cultivated rice an area that also includes Nepal, Bhutan, northeastern India (Assam),Myanmar, L aos and northern Thailand (Chang, 1976; 1985;Wang and Sun, 1996; Zeng et al ., 1998). China has accumu-lated tremendously rich genetic diversity in the rice gene pool through thousands of years of cultivation and selec-tion by local farmers in v arious agro-ecosystems. As a result,a great number of rice landraces have been widely culti-vated in this country, particularly in its southern parts.According to the statistics of the Institute ｏf Crop Germplasm Resources, Chinese Academy of Agricultural Sciences, more than 76 600 accessions of rice germplasm were collected through nationwide germplasm explorations during the last 50 years, and among these, over 53 300accessions were landraces (Ying, 2000).Yunnan is a mountainous province, in the southwest of China, containing the country’s greatest level of plant and animal species diversity. It is also the most diverse region in China in terms of its geographical landscapes, climatic conditions, agricultural ecosystems, biological diversity,and endemic ethnic cultures. A remarkably diverse set of rice landraces, i ncluding upland and lowland, glutinous and non-glutinous, and Indica and Japonica varieties, was found in Yunnan Province (Zhang et al., 2001). These rice varieties have played a very important role in the local food security and sustainable development of agriculture, in addition to their significant values as genetic resources for rice genetic improvement (Lu and Zhu, 1995; Li a nd Rutger,2000; T ang, 2002).However, with t he increasing challenge of f ood security,rice production in Yunnan, as in many other rice-growing regions in China, followed a h igh input and output model inＺＨＵ Ｍｉｎｇ－Ｙｕ ｅｔ ａｌ．：Ｅｓｔｉｍａｔｉｎｇ Ｇｅｎｅｔｉｃ Ｄｉｖｅｒｓｉｔｙ ｏｆ Ｒｉｃｅ Ｌａｎｄｒａｃｅｓ ｆｒｏｍ Ｙｕｎｎａｎ ｂｙ ＳＳＲ Ａｓｓａｙ ａｎｄ Ｉｔｓ Ｉｍｐｌｉｃａｔｉｏｎ ｆｏｒＣｏｎｓｅｒｖａｔｉｏｎ１４５９the past decades to achieve its high yield. Undoubtedly, the intensive agricultural practice of the cultivation of im-proved high-yielding modern rice v arieties on an extensive acreage contributed remarkably to the increase in local food production. However, it also resulted in significant “ge-netic erosion” the loss of traditional varieties from agro-ecosystems (Porceddu et al., 1988; Singh, 1999) in the rice gene pool, in addition to the deterioration of the rice ecological systems. The loss of genetic diversity has con-siderably hindered our efforts for consistently high pro-duction and further improvement of rice varieties adapting to various biotic and abiotic stresses that can significantly reduce productivity of rice varieties. All of these together will t hreaten long-term food s ecurity in t he region. T herefore, strategic conservation of genetic resources in the rice gene pool has become increasingly important for ensuring the sustainable production of this food crop.For the effective conservation of rice genetic resources, a clear understanding of differentiation and relationships of rice varieties from a targeted region is essential for deter-mining the appropriate sampling and management procedures. Traditional customs of rice cultivation and management in relation to other crops, the frequency and intensity of rice varietal exchanges among villages and regions, and cultural practices that would influence the availability of a certain type of rice varieties, all need to be understood. One of the important parameters for effective genetic conservation is to detect the allelic richness of the population or samples that are targeted for conservation. Molecular marker technology is one of the powerful tools for determining genetic variation in rice varieties (Xu and Wang, 1974; Zhang et al., 1992; Lu and Zhu, 1995; Zeng and Zheng, 2001; Lu et al., 2002), in addition to the under-standing of relationships between genetic diversity and culture aspects of rice, which would facilitate the effective conservation of genetic resources in the rice gene pool by strategic d ecision-making.Simple sequence repeats (SSR), also referred to as microsatellites, are useful markers for studying genetic dif-ferentiation and relationships, because of the significant level of allelic polymorphisms that can be readily revealed (Ishii et al., 2001). Polymorphisms in the microsatellite re-gions are considered to be the result of mis-replication of repeated sequences (Richards and Sutherland, 1994). The resultant polymorphisms can be detected by PCR amplifi-cation using pairs o f primers specific to the sequences flank-ing the microsatellite repeats. Microsatellite markers are supposed to be particularly suitable for evaluating genetic diversity and relationships among closely related plant accessions or individuals, such as different rice cultivars (Akagi et al., 1997; Guo and Zhao, 1998). To date, more than 2 500 SSR primer pairs have been developed in rice (McCouch et al., 2002), which provides a tremendous op-portunity for gaining an insight into the genetic structure of the rice genome.The objective of this study was to determine the pattern of genetic differentiation of rice landraces collected from the selected sites, representing the medium-developed ag-ricultural regions in Yunnan Province, where modern im-proved and traditional rice varieties are grown simultaneously. This knowledge would allow estimation of the values of local rice conservation programs, particularly for on-farm management practices.１ Ｍａｔｅｒｉａｌｓ ａｎｄ Ｍｅｔｈｏｄｓ1.1 Plant materialsA total of 85 rice (Oryza sativa L.) accessions were used in this study for the SSR analysis, including Indica and Japonica ecotypes, as well as glutinous and non-gluti-nous varieties. Most of the varieties were local landraces commonly cultivated in Yunnan Province. Of these, 74 ac-cessions were collected directly from farmer households scattered randomly in 16 villages belonging to two coun-tries in 2002, and eight accessions were collected from an-other village of Luxi County in the previous year (Table 1). Three rice accessions, IR36, IR64 (from the Philippines), and Nihonbare (originally from Japan) donated by the In-ternational Rice GeneBank of the International Rice Re-search Institute (IRRI) at Philippines, were used as the stan-dard varieties representing the typical Indica and Japonica ecotypes, respectively. Owing to the highly homogeneous nature of rice varieties, particularly the traditional varieties, one seed randomly selected from each accession was in-cluded in the analysis to represent the variety.1.2 D NA extraction and PCR assayDNA samples were extracted from leaf tissues of a single seedling at about the three-leaf stage, using the CTAB method described by Song et al. (2003). A total number of 19 SSR primer pairs were selected to analyze genetic poly-morphisms in the rice varieties (Table 2), based on the RiceGenes Database (/). Primer pairs w ere chosen based on the number of alleles in each locus with relatively high polymorphisms. The PCR reactions were performed in a PTC 10096 V thermocycler (MJ Research Inc., Watertown, M ass) programmed following the descrip-tion by Wu and Tanksley (1993). A denaturation period o f 4 min at 94 °C was followed by 36 cycles of 40 s at 94 °C, 30 s at 55 °C, and 40 s a t 72 °C, and then 10 min at 72 °C for the１４６０Ａｃｔａ Ｂｏｔａｎｉｃａ Ｓｉｎｉｃａ 植物学报 Ｖｏｌ．４６ Ｎｏ．１２ ２００４Table 1 Rice genetic resources used for the simple sequence repeat (SSR) analysis with information on their eco-types and origin in Yunnan Province, except for the typical Indica IR36, IR64, and Japonica Niponbare. Landraces collected as the same variety names but from different sites were identified by giving different numbers following the variety namesV ariety Eco-type(1)Code Locality (Village/Town/County)Note(2) Jinyougui-99Indica JYG-99-I Y angjie/Xinshao/MileY unhui-290Indica YH-290-I Y angjie/Xinshao/MileGangyou-225Indica GY-225-I Y angjie/Xinshao/MileTeqing Indica TQ-I Y angjie/Xinshao/MileDiantuan-502-1Indica DT-502-1-I Y angjie/Xinshao/MileSiyou Indica SY-I Donghong/Donghong/MileDiantuan-502-2Indica DT-502-2-I Donghong/Donghong/MileHongcheng Indica HC-I Donghong/Donghong/MileHongyou Indica HY-I Donghong/Donghong/MileGuichao Japonica GC-I Donghong/Donghong/MileHuangkenuo-1Japonica HKN-1-J Donghong/Donghong/Mile G Hongzayou Indica HZY-I Donghong/Donghong/MileJingdao-1Japonica JD-1-J Donghong/Donghong/MileXiandaonuo-1Indica XDN-1-I Gucheng/Guishan/Xinping G Xianggu Indica XG-I Gucheng/Guishan/XinpingY unuo-22Indica YN-22-I Gucheng/Guishan/Xinping G Jingdaoyunyou-4Japonica JDYY-4-J Gucheng/Guishan/XinpingGangyou-22Indica GY-22-I Gucheng/Guishan/XinpingEshandabagu Indica ESDBG-I Xiguan/Guishan/XinpingHuangkenuo-2Japonica HKN-2-J Xiguan/Guishan/Xinping G Langanwuzui-1Indica LGWZ-1-I Dabeimen/Guishan/XinpingXinyu-1Indica XY-1-I Dabeimen/Guishan/XinpingLanganwuzui-2Indica LGWZ-2-I Gepeng/Gepeng/XinpingJindao-1Japonica JD-1-J Gepeng/Gepeng/XinpingNuogu-1Indica NG-1-I Gepeng/Gepeng/XinpingGanyou-12Indica GY-12-I Gepeng/Gepeng/XinpingXiandaonuo-2Indica XDN-2-I Gepeng/Gepeng/Xinping G Hongta-4Indica HT-4-I Gepeng/Gepeng/XinpingTaibai-8Japonica TB-8-J Gepeng/Gepeng/XinpingAixianlaopinzhong Indica AXLPZ-I Gepeng/Gepeng/XinpingNuogu-2Indica NG-2-I Tala/Gucheng/XinpingAijiaonuo Japonica AJN-J Mangan/Pingzhang/Xinping G Bingmangu Indica BMG-I Mangan/Pingzhang/XinpingGuangtougu Japonica GTG-J Mangan/Pingzhang/XinpingHeizinuo Indica HZN-I Mangan/Pingzhang/Xinping G Hongxinnuo Indica HXN-I Mangan/Pingzhang/Xinping G Mojiangnuo Indica MJN-I Mangan/Pingzhang/Xinping G Qidaigu Indica QDG-I Mangan/Pingzhang/XinpingRuandao Indica RD-I Mangan/Pingzhang/XinpingShanyounuo Indica SYN-I Mangan/Pingzhang/Xinping G Xiaohuanuo Indica XHN-I Mangan/Pingzhang/Xinping G Yidalinuo Indica YDLN-I Mangan/Pingzhang/Xinping G Y uanjiangnuo Indica YJN-I Mangan/Pingzhang/Xinping G Daxiangnuo Indica DXN-I Fuku/Pingzhang/Xinping G Shuijia-99Indica SJ-99-I Fuku/Pingzhang/XinpingBeizinuo Japonica BZN-J Cangfang/Pingzhang/Xinping G Cuoluonuo Japonica CLN-J Cangfang/Pingzhang/Xinping G Dabaigu Indica DBG-I Cangfang/Pingzhang/XinpingLaoluochuan Indica LLC-I Cangfang/Pingzhang/XinpingLengshuiluochuan Indica LSLC-I Cangfang/Pingzhang/XinpingMaidao Indica MD-I Cangfang/Pingzhang/XinpingBailengshui Japonica BLS-J Shanglongtan/Pingzhang/XinpingHeilengshui Japonica HLS-J Shanglongtan/Pingzhang/XinpingＺＨＵ Ｍｉｎｇ－Ｙｕ ｅｔ ａｌ．：Ｅｓｔｉｍａｔｉｎｇ Ｇｅｎｅｔｉｃ Ｄｉｖｅｒｓｉｔｙ ｏｆ Ｒｉｃｅ Ｌａｎｄｒａｃｅｓ ｆｒｏｍ Ｙｕｎｎａｎ ｂｙ ＳＳＲ Ａｓｓａｙ ａｎｄ Ｉｔｓ Ｉｍｐｌｉｃａｔｉｏｎ ｆｏｒＣｏｎｓｅｒｖａｔｉｏｎ１４６１final extension. Reactions were carried out in a volume of20 µL c ontaining 1125widthＡｃｔａ Ｂｏｔａｎｉｃａ Ｓｉｎｉｃａ 植物学报 Ｖｏｌ．４６ Ｎｏ．１２ ２００４１４６２accessions were quantified according to Nei (1978). Rela-tionships of the rice varieties were estimated based on the similarity coefficient using the UPGMA clustering method. The UPGMA tree was constructed using the NTsyspc pro-gram ver. 20.2a (Rohlf, 1994).２ ＲｅｓｕｌｔｓAll of the 19 selected rice SSR primer pairs amplified visible DNA bands from the included rice varieties and no null alleles were detected. Most of the varieties had a unique genotype. A total of 83 SSR alleles, with molecular weights ranging from 100 to 500 bp, were scored from the 85 rice varieties (Fig.1; Table 2). The highest number (7) of alleles was scored from the locus RM21 and the lowest (3 alleles) was found from the loci RM55, RM211, RM212, RM215, and RM253 in the 85 rice samples (Table 2). The selected SSR primer pairs generated an average of 4.37 alleles per locus and no monomorphic locus was observed in the in-cluded rice samples.A UPGMA dendrogram based on the cluster analysis of Nei’s (1978) unbiased genetic similarity of the SSR alleles was constructed for all the rice varieties. The cluster analy-sis showed a significant genetic variation among the in-cluded rice varieties with similarity coefficients varyingTable 2 The SSR primer pairs used for genetic diversity study of 84 rice varieties Locus LOC(1)Primer sequence(2)(5＇ＺＨＵ Ｍｉｎｇ－Ｙｕ ｅｔ ａｌ．：Ｅｓｔｉｍａｔｉｎｇ Ｇｅｎｅｔｉｃ Ｄｉｖｅｒｓｉｔｙ ｏｆ Ｒｉｃｅ Ｌａｎｄｒａｃｅｓ ｆｒｏｍ Ｙｕｎｎａｎ ｂｙ ＳＳＲ Ａｓｓａｙ ａｎｄ Ｉｔｓ Ｉｍｐｌｉｃａｔｉｏｎ ｆｏｒＣｏｎｓｅｒｖａｔｉｏｎ１４６３between 0.152 and 0.900 (Fig.2). The d endrogram revealed two distinct groups at the similarity coefficient level of 0.152. Interestingly, the two groups of the 85 rice varieties were clearly associated with their ecotypes, in other words,all the accessions of Indica ecotype, including the stan-dard varieties IR34 and IR 64, were included in one group (upper cluster in Fig.2), w hereas the accessions of Japonica ecotype, including t he Nihonbare, were included in another group (lower cluster in Fig.2). There was only one excep-tion that an Indica accession (HC-I) was included in the Japonica group. A slightly greater genetic variation was observed among the Indica varieties than among the Japonica varieties by a brief comparison. The glutinous rice varieties were randomly scattered among the Indica and Japonica varieties without a particular differentiation pattern, indicating their i ndependent origin. Genetic differ-entiation of the rice accessions seemed to have a weak association with their village of origin. Only some rice ac-cessions collected from the same villages showed a rela-tively close g enetic relationship. I n general, a relatively high level of genetic diversity was detected in rice landraces from Pingzhang Township of Xinping County, because these landraces were scattered among different groups and subgroups in the dendrogram.It is noteworthy that the accessions labeled with the same names but collected from different villages, so Huangkenuo (HKN-1, H KN-2, and HKN-3), Nuogu (NG-1and NG-2), and Langanwuzui (NGWZ-1 and LGWZ-2) did not show identical genetic variation pattern, indicating a considerable differentiation among the accessions identi-fied as the same varieties. The two accessions ofAijiaohonggu with different panicle colors, and identified as AJHGW (white) and AJHGR (red), also demonstrated a considerable genetic variation (Fig.2), suggesting the dis-crepancy of genetic identity and varietal names of some rice varieties.３ ＤｉｓｃｕｓｓｉｏｎThe effective and strategic conservation of genetic di-versity in the rice gene pool relies essentially on the under-standing of genetic diversity patterns of rice varieties in a target region, including their levels and distribution of the diversity (Zeng et al., 1998; Zhang, 2001; Lu et al ., 2002).This is particularly important for in situ conservation of rice genetic diversity on farm management (or on-farm conservation), because the combination of f armers’ diverse needs together with the cultivation of varieties in different ecosystems has created and accumulated wide genetic variation. The continued cultivation and management of different rice varieties by farmers would promote the con-tinued availability of rice biodiversity in various rice eco-systems (Zhu et al., 2003).Results from this study evidently indicated that genetic variation of rice varieties in the target region of Yunnan Province is s till remarkably rich, particularly among the tra-ditional varieties, although only a relatively small set of rice varieties was screened from three counties of a randomly selected region in this analysis. This is the direct evidence of maintaining rice diversity through farmer’s cultivation and management. The considerably rich genetic diversity of rice varieties in Yunnan Province could be attributed to its complicated local geographical conditions where differ-ent farming practices and ago-ecosystems exist. The diver-sity may also be significantly associated with its rich eth-nic and culture diversity that promotes m iscellaneous needs and applications of rice varieties. It is therefore very impor-tant to have more thorough studies of farmer’s rice culture at specific locations and its roles in maintaining genetic diversity of rice varieties, which provides us a road-map for strategic conservation of rice g enetic resources. In addition,local people have diverse dietary habits for rice products,such as different types of rice noodles, rice cakes, rice wines,and rice bread, which maintains the diversification of rice varieties (Zeng et al ., 1998; Zhang et al ., 2001). More fol-low-up investigations of such aspects in the target areas need to be conducted. Relative isolation of these areas has probably played a considerable role in reducing the speed of popularization and exchange of modern improved rice varieties. Which of the factors have played an essential role in maintaining the genetic diversity of Yunnan riceFig.1. SSR amplification products generated by the primer pair RM84. Lanes 1－21 represent XY-1-I, HX-39-J, YJN-I, HX-41-J, SY-I, GC-I, XDN-1-I, NG-2-I, HC-I, JD-2-J, HKN-3-J, BZG-J, HY-I, DBG-I, YDLN-I, JDYY-4-J, XG-I, XHN-I, ALN-J,MLXG-J, IR36, IR64, and NIP. M, pUC19DNA/Msp )markers. Codes of the rice varieties refer to those in Table 1.Ａｃｔａ Ｂｏｔａｎｉｃａ Ｓｉｎｉｃａ 植物学报 Ｖｏｌ．４６ Ｎｏ．１２ ２００４１４６４Fig.2. A dendrogram showing relationships of Yunnan rice varieties based on the cluster analysis of Nei’s (1978) unbiased genetic identity of 83 SSR alleles. A significant genetic variation and the clear grouping between Indica-Japonica ecotypes are indicated. Codes of the rice varieties refer to those in Table 1.ＺＨＵ Ｍｉｎｇ－Ｙｕ ｅｔ ａｌ．：Ｅｓｔｉｍａｔｉｎｇ Ｇｅｎｅｔｉｃ Ｄｉｖｅｒｓｉｔｙ ｏｆ Ｒｉｃｅ Ｌａｎｄｒａｃｅｓ ｆｒｏｍ Ｙｕｎｎａｎ ｂｙ ＳＳＲ Ａｓｓａｙ ａｎｄ Ｉｔｓ Ｉｍｐｌｉｃａｔｉｏｎ ｆｏｒＣｏｎｓｅｒｖａｔｉｏｎ１４６５varieties? More detailed studies of different sorts would be accessory to determine these. This study that revealed a significant level of genetic diversity has clearly demon-strated the importance of continued in situ conservation of traditional rice varieties suitable for various purposes in different regions of Yunnan.Data revealed by the cluster analysis of genetic similar-ity of the 85 rice varieties based on the SSR variation pat-tern provided particularly useful information for the effec-tive conservation of r ice genetic d iversity in the target region. Since the 19 SSR primer pairs can amplify DNA fragments representing each chromosome, the diversity pattern re-vealed by these SSR loci is meaningful. It is evident that genetic diversity of the rice varieties is not evenly distrib-uted in the sampled region, which indicated different ge-netic relationships of these rice varieties. This suggests that an appropriate sampling strategy based on the genetic variation pattern should be f ollowed to guarantee the maxi-mum capture of rice genetic diversity in the given regions. Therefore, the selection of traditional rice varieties for con-servation should not be performed on a random basis; instead, they should be selected according to the variation pattern indicated by genetic studies. In other words, a quick pre-screen of genetic differentiation and relationships of rice varieties based on a small sample size (e.g. one seed representing a variety) should be conducted before the actual collection of these varieties for ex situ conservation. This will provide a sound basis for a possible capturing of maximum genetic d iversity i n the t arget regions. For example, it was shown that some areas like Pingzhang township in Xinping County possessed a slightly higher level of diver-sity than the other areas based on the SSR analysis, a com-paratively large number o f varieties should be included from such areas for conservation.It should also be pointed out that traditional rice variet-ies given the same name by local farmers might not neces-sarily be the same varieties or the same genotypes. Results from this study indicated that some varieties labeled with the same varietal names by farmers in different villages or counties, in fact, represented significantly different genotypes. For instance, the varieties named by farmers as Huangkenuo, Nuogu, and Langanwuzui collected from dif-ferent villages actually demonstrated rather distant genetic relationships. The variety AJHG with white and r ed panicles also showed considerable differentiation. The genetic rela-tionships of such varieties should be closely investigated. Therefore, during the sampling p rocess, if we exclude those varieties labeled with the same names from different localities, we may lose a considerable amount of genetic diversity. On the contrary, some varieties with different varietal names, s uch as YN-22-I versus E SDBG-I and MJN-I versus XHN-I showed a very close genetic relationship. Their varietal status needs to be confirmed by tracing their sources and origin. At least in the sampling process, variet-ies sharing such a close genetic relationship should not all be included for conservation.Furthermore, this study also demonstrated the useful-ness of SSRs as molecular markers in determining genetic diversity of rice landraces collected from Yunnan. It is im-portant to point out that the SSR markers involved in this study can distinguish the Indica and Japonica varieties unambiguously. It is usually difficult to accurately identify the Indica and Japonica ecotypes of rice by their morpho-logical characteristics, and sometimes even by their isozyme variation patterns (Li and Rutger, 2000; Tang, 2002). The correct determination of the two ecotypes has a significant value in rice breeding programs for selecting the desired rice germplasm. Therefore, the great potential of employ SSR analysis for accurate identifying the Indica and Japonica ecotypes should be thoroughly explored by in-clusion of a set of appropriately selected SSR primer pairs, in addition to a wider range of well defined Indica and Japonica rice germplasm for confirmation. Acknowledgements: The first author would like to ex-press his sincere appreciation to Dr. SONG Zhi-Ping of Fudan University for his assistance in the SSR experiment and to Mr. PENG Lei of Y unnan A gricultural University for his help in collecting rice germplasm in Yunnan.Ｒｅｆｅｒｅｎｃｅｓ：Akagi H, Yokozeki Y, Inagaki A, Fujimura T. 1997. Highly poly-morphic microsatellites of rice consist of AT repeats, and a classification o f closely related cultivars with these microsatellite loci. Theor Appl Genet, 94: 61－67.Chang T T. 1976. The origin and evolution, cultivation, dissemi-nation and diversification of Asian and African rices. Euphytica, 25: 425－441.Chang T T. 1985. Crop history and genetic conservation: riceＡｃｔａ Ｂｏｔａｎｉｃａ Ｓｉｎｉｃａ 植物学报 Ｖｏｌ．４６ Ｎｏ．１２ ２００４１４６６Litt M, Luty J A, 1989. Hypervariable microsatellite revealed by in vitro amplification of a dinucleotide repeat within the car-diac muscle action gene. Am J Human Genet, 44: 391－401. Lu C-F (陆朝福), Zhu L-H (朱立煌). 1995. Molecular marker assisted selection in plant breeding. Prog Biotech (生物工程进展), 15: 11－17. (in Chinese with English abstract)Lu B R, Zheng K L, Qian H R, Zhuang J Y. 2002. Genetic differentiation of wild relatives of rice as referred by the RFLP analysis. Theor Appl Genet, 106: 101－106.Martin C, Juliano A, Newbury H J, Lu B R, Jackson M T, Ford-Lloid B V. 1997. The use of RAPD markers to facilitate the identification of Oryza species within a germplasm collection.Genet Resour Crop Evol, 44: 175－183.McCouch S R, Teytelman L, Xu Y B, Lobos K B, Clare K, Walton M, Fu B, Maghirang R, Li Z K, Xing Y Z, Zhang Q F, Kono I, Yano M, Fjellstrom R, DeClerck G, Schneider D, Cartinhour S, Ware D, Stein L, 2002. Development and map-ping of 2 240 new SSR markers for rice (Oryza sativa L.).DNA Res, 9: 199－207.Nei M. 1978. Estimation of average heterozygosity and genetic distance from a small number of individuals. Genetics, 89: 583－590.Rohlf F J. 1994. NTSYS-pc, numerical taxonomy and multivari-ate analysis system. ver. 1.80. Exeter Software, New York. Porceddu E, Ceoloni C, Lafiandra D, Tanzarella O, Scarascia A, Mugnoza G T. 1988. Genetic resources and plant breeding: problems and prospects. Miller T E, Koebner R M D. Pro-ceedings of the 7th International Wheat Genetiｃｓ Ｓｙｍｐｏｓｉｕｍ．Ｃａｍｂｒｉｄｇｅ， ＵＫ： Ｉｎｓｔｉｔｕｔｅ ｏｆ Ｐｌａｎｔ Ｓｃｉｅｎｃｅ Ｒｅｓｅａｒｃｈ Ｐｒｅｓｓ． ７－２１．Richards R, Sutherland G R. 1994. Simple repeat DNA is not replicated simply. Nat Genet, 6: 114－116.Singh R K. 1999. Genetic resource and the role of internationalcollaboration in rice breeding. Genome, 42: 635－641.Song Z P, Xu X, Wang B, Chen J K, Lu B R. 2003. Genetic diversity in the northernmost Oryza rufipogon populations estimated by SSR markers. Theor Appl Genet, 107: 1492－1499.Tang S-X, Jiang Y-Z, WeiX-H , L iZ-C, YuH-Y. 2002.Genetic diversity of isozymes of cultivated rice in China. Acta Agron Sin (作物学报), 28: 203－207. (in Chinese with En-glish abstract)Wang X-K (王象坤), Sun C-Q (孙传清). 1996. Origin and Differ-entiation of Chinese Cultivated Rice. Beijing: China Agricul-tural University Press. (in Chinese)Xu X-H (徐祥浩), Wang G-C (王国昌), Zheng X-B (郑小波), Wang H-X (王焕校). 1974. A report on the vertical distribu-tion of the rice varieties in Simao, Yunnan. Acta Bot Sin (植物学报), 16: 208－222. (in Chinese with English abstract) Ying C-S (印存山). 2000. Conservation and utilization of rice genetic resources in China. Chin Rice Res Newsl (中国水稻研究通报), 8: 13－14. (in Chinese with English abstract) Zeng L-J (曾莉娟), Zheng C-M (郑成木). 2001. SSR technique and its application. Chin J Trop Agr (热带农业科学), 91: 56－59. (in Chinese)Zeng Y, Wang J, Li X. 1998. Genetic variation of crop resources in Yunnan Province, China. Plant Genet Resour Newsl, 114: 40－42.Zhang H, Shen S, W ang X, Zeng Y, Li Z, Yang Z. 2001. Ecological and genetic diversity of rice germplasm in Yunnan, China.PGR Newsl, 125: 24－28.Zhu Y Y, Wang Y Y,Chen H R, Lu B R. 2003. Conserving tradi-tional rice through biodiversity management. BioScience, 53: 158－162.（Ｍａｎａｇｉｎｇ ｅｄｉｔｏｒ： ＺＨＡＯ Ｌｉ－Ｈｕｉ）。