用杀线虫黑曲霉 应变控制植物寄生线虫

(Received June 18, 1993; accepted August 27, 1993) Abstract--An isolate of Aspergillus niger (designated PD42) was evaluated in laboratory, greenhouse, and held trials for efficacy in controlling plantparasitic nematodes. In greenhouse experiments, PD-42 drenches containing spores of PD-42 on oatmeal significantly reduced galling on tomato due to root-knot nematode as compared to untreated controls. In a one-half acre held experiment, PD-42 incorporated in seed coats was associated with signihcantly increased yield and decreased root-knot galling on pepper. In a second one-half acre field experiment, PD-42 drenches significantly reduced tomato and pepper root galling due to Meloidogyne incognita, and nonsignificant yield increases occurred. In each field experiment, treatment with PD-42 reduced Rotylenchulus reniJbrmis populations. The nematicidal components of the A. niger culture filtrates include citric acid, oxalic acid, and undetermined molecules larger than 8000 MW. Key Words--Aspergiflus niger, biological control, plant-parasitic nematodes, Meloidogyne incognita, nematicidal activity, Caenorhabditis elegans, Roty-
METHODS AND MATERIALS
Organisms. The A. niger strain in these experiments produces black spores and is referred to by its coded designation PD-42. PD-42 was the most abundant fungus encountered from the chinampa agricultural soils (Zuckerman et al., 1989). Nematicidal Aspergillus with green, brown, or yellow spores were also frequently isolated, but PD-42 showed the highest activity against plant nematodes in greenhouse tests and was selected for further study. PD-42 was maintained in cryopreservation buffer at - 8 0 ° C and under liquid nitrogen. When required for experiments, it was grown on potato dextrose agar (PDA) or in potato dextrose broth (PDB). Meloidogyne incognita (Kofoid and White) race 3 was obtained from Dr. M. McClure, University of Arizona, Tucson, and was maintained on tomato (Lycopersicon esculentum L.) cv. Rutgers in the greenhouse. Inoculum for greenhouse experiments consisted of eggs obtained by the method of Hussey and Barker (1973). The free-living nematode Caenorhabditis elegans Dougherty and Calhoun for in vitro studies of nematicidal activity were cultured axenically at 22°C on heme medium (McClure and Zuckerman, 1982). Tomato cv. Floradade and pepper (Capsicumfrutescens L.) cv. Cubanelle were used in the field trials. Laboratory Assays for Nematicidal Activity. The nematicidal activity of PD-42 was first observed in an assay in which C. elegans was placed in proximate contact with the fungus in an agar plate (Zuckerman et al., 1989). This procedure was followed by a similar in vitro assays of the effect on second stage larvae of M. incognita. The criterion for high nematicidal activity was death of the worms within 24 hr. Culture filtrates of A. niger, or the acid components
Journal of Chemical Ecology, VoL 20, No. 1, 1994
CONTROL OF PLANT-PARASITIC NEMATODES BY A NEMATICIDAL STRAIN OF Aspergillus niger
B.M.
ZUCKERMAN,
I'* M. MATHENY, I and N. ACOSTA 2
lenchulus reniformis.
INTRODUCTION A n early o b s e r v a t i o n o f toxicity o f Aspergillus to n e m a t o d e s w a s m a d e b y H a v e n M e t c a l f (1903). In this p a p e r , w h i c h , to o u r k n o w l e d g e , also r e c o r d s t h e first s u c c e s s f u l a t t e m p t to p r o d u c e a n a x e n i c c u l t u r e o f n e m a t o d e s , M e t c a l f d e s c r i b e s t h e lethal effect o f a b l a c k - s p o r e d Aspergillus o n Rhabditis brevispina (Claus) Butschli. H e w r o t e " N o i n v e s t i g a t i o n w a s m a d e o f t h e b y - p r o d u c t s o f this
suggested be fruitful if followed out with reference to certain pathogenic nematodes?" Later, other references to the nematicidal affects of Aspergillus and its filtrates appeared, among them reports by Murad (1966), Mankau (1969), Alam et al. (1973), and Khan et al. (1981). The chinampa agricultural soils of Mexico contained organisms that exert a suppressive effect on plant-pathogenic fungi (Lumsden et al., 1987) and plantparasitic nematodes (Zuckerman et al., 1989). The predominant nematicidal fungi from these soils were species of Aspergiltus which, in agar culture, produced green, yellow, black, or brown spores. Of these, the most toxic isolate was identified by M. Bigelow, University of Massachusetts, as a strain of Aspergillus niger van Tieghem (coded PD-42). The current paper reports on laboratory, greenhouse, and field studies to examine the nematicidal properties of this A. niger isolate on plant-parasitic nematodes.