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Genetics

Isozyme Analysis to Differentiate Species of Peronosclerospora Causing Downy Mildews of Maize. M. R. Bonde, Research plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, Plant Disease Research Laboratory (PDRL), Fort Detrick, Building 1301, Frederick, MD 21701; G. L. Peterson(2), W. M. Dowler(3), and B. May(4). (2)(3)Biological laboratory technician, and research plant pathologist, respectively, U.S. Department of Agriculture, Agricultural Research Service, Plant Disease Research Laboratory (PDRL), Fort Detrick, Building 1301, Frederick, MD 21701; (4)Director, Cornell Laboratory for Ecological and Evolutionary Genetics, Cornell University, Ithaca, NY 14853. Phytopathology 74:1278-1283. Accepted for publication 22 May 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/Phyto-74-1278.

Isozymes from 10 fungal cultures representing three species of the genus Peronosclerospora were compared electrophoretically on starch gels to determine if isozyme analysis can be used to aid in species identification. Cultures of P. sorghi from Texas (United States), southern India, and Brazil were nearly identical with apparent polymorphisms (allelic variations) at three of 13 presumed loci examined. Of 15 apparent alleles detected in an isolate of P. sorghi from Thailand, only four were in common with alleles in any of five 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 most likely of the same species. In four cultures of the P. sacchari- P. philippinensis complex, apparent polymorphisms were evident in six of 13 loci examined. Considerable potential for variation exists in this “species.” 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 average coefficient of similarity of 0.50 was estimated by comparing the Thailand culture with P. sacchari and P. philippinensis at 13 loci. Isozyme analysis is useful for distinguishing species of Peronosclerospora and elucidating phylogenetic relationships.