Isozyme analysis to differentiate species of Peronosclerospora causing downy mildews of maize.
Isoenzymes from 10 fungal cultures representing 3 P. spp. were compared electrophoretically on starch gels to determine if isoenzyme analysis can be used to aid in spp. identification. Cultures of P. sorghi from Texas, southern India and Brazil were nearly identical with apparent polymorphisms (allelic variations) at 3 of 13 presumed loci examined. Of 15 apparent alleles detected in an isolate of P. sorghi from Thailand, only 4 were in common with alleles in any of 5 other cultures of typical P. sorghi. Two cultures of P. philippinensis from the Philippines and one of P. sacchari from Taiwan had all 16 alleles in common indicating that they are probably the same sp. In 4 cultures of the P. sacchari-P. philippinensis complex, apparent polymorphisms were evident in 6 of 13 loci examined and thus considerable potential for variation exists. The isolate of P. sorghi from Thailand was more closely related to the P. sacchari-P. philippinensis complex than to the other isolates of P. sorghi. An av. coefficient of similarity of 0.5 was estimated by comparing the Thailand culture with P. sacchari and P. philippinensis at 13 loci. Isoenzyme analysis is useful for distinguishing spp. of P. and elucidating phylogenetic relationships.