A Simplified Medium for Monoxenic Culture of Pratylenchus penetrans and Ditylenchus dipsaci.

P r e s e n t m e t h o d s o f establishing and m a i n t a i n i n g monoxenic cultures of plant parasitic nematodes are laborious. Use of complex, multicomponent nutrient media for production of callused host tissues is a factor c o n t r i b u t i n g to the inefficiency of these methods. For example, tile most commonly used of these media contains 19 constituents (1) . This n o t e r e p o r t s maintenance of Pratylenchus penetrans and an onion race of Ditylenchus dipsaci on callus tissue produced with simplified nutrient agar. W e e k o l d , s ter i le onion (Allium cepa 'Aristocrat ') and alfalfa seedlings (Medicago sativa ' R a n g e r ' ) produced by previously described methods (2) were cultured for 2 weeks on nutrient medium (20 g sucrose, 5 g yeast extract [Difco Laboratories, Detroit, Mich.], 2 mg 2,4-dichlorophenoxyacetic acid, 10 g Difco-Bacto agar, 1000 ml distilled water) in 25 X 150 mm tubes. Thereafter, onion and alfalfa callus tissues were inoculated with D. dipsaci and P. penetrans, respectively. Cultures were maintained in the dark at 23 C. D. dipsaci were extracted from each of ten 8-week-old cul tures with modified Baermann funnels. Nematodes in three l-ml aliquots were counted. N u m b e r s of P. penetrans in 10-week-old cultures were determined similarly. Populations of D. dipsaci produced by these m e t h o d s r anged f r o m 500 to 23 ,300 n e m a t o d e s / c u l t u r e t u b e . The average population was 10,500/tube. Culture tubes infested with P. penetrans contained an average of 20,460 nematodes. Populations ranged from 8,800 to 40,000/tube. These tests have been repeated with similar results. Populations of D. dipsaci and P. penetrans rea red in ou r l abora to r i e s by standard procedure on Krusberg's medium ( l ) average a p p r o x i m a t e l y 2 0 , 0 0 0 and 36,000/tube, respectively (2). Thus, reproduction of these nematodes on simplified medium, although lower, compares well with the average rates attained with previous methods. Because of the time savings inherent in its production, the simplified medium affords a useful culture substrate in teaching and research applications where maximum population development is not required. M o r e o v e r , since maximum populations developed on the simplified medium were comparable to the best reproduction rates expected with Krusberg's medium, further development of the simplified medium could result in a simple culture substrate capable of supporting excellent nematode reproduction.