ALLOZYME ANALYSIS OF AUSTRALIAN ISOLATES OF DILOPHOSPORA-ALOPECURI

Twenty-one isolates of the nematode-vectored plant pathogen, Dilophosp ora alopecuri, were examined by allozyme electrophoresis. The study fo cused on isolates from Australia, including those associated with popu lations of the seed-gall nematode, Anguina funesta, in Western Austral ia (W.A.), where the fungus apparently provides natural control of the A. funesta-Clavibacter toxicus association responsible for annual rye grass toxicity, and a range of Anguina populations in south-eastern Au stralia. Reference strains from international culture collections were included. Variation was found in 26 of 27 presumptive loci and 10 ele ctrophoretic types were identified. All Australian isolates fell into six electrophoretic types that formed two groups of three that differe d by less than 13% within each group, but differed by over 70% between the groups. Of the isolates from W.A., six fell into one electrophore tic type and one into a second electrophoretic type that differed at o ne locus only. Three exotic isolates varied from Australian ones by 27 -74%. Dilophospora alopecuri exhibited greater within-species allelic variation than previously reported for asexually-reproducing halophase fungi. The lack of variation within W.A. suggests that (i) a teleomor ph does not occur under local conditions, (ii) the W.A. population has arisen from a single introduction and (iii) selection of strains suit able for biocontrol of Anguina funesta and Clavibacter toxicus should include material from eastern Australia.