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Genetics

Isozyme Variability in Alternaria solani and A. alternata. D. M. Petrunak, Graduate student, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; B. J. Christ, Associate professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 82:1343-1347. Accepted for publication 30 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1343.

Fifty-four isolates of Alternaria solani, the causal agent of early blight of potato, and 96 isolates of A. alternata from various hosts and geographic locations were examined for isozyme variability; starch gel electrophoresis was used for the analyses. Thirteen loci were identified in 10 enzyme systems. Thirty-five electrophoretic types (ETs) were detected. The most common ET had 47 isolates, whereas 18 ETs had only one isolate. The average genetic diversity for a given enzyme ranged from 0.000 to 0.763; the average genetic diversity was 0.500. The number of alleles detected per enzyme ranged from one to four; the average was 2.9. Cluster analysis divided the isolates into groups that almost completely corresponded to species. Only one isolate of A. alternata did not fit this pattern. Three enzymes differentiated the isolates according to species for all but one of the isolates. No significant correlation was found between isozyme phenotype and host or geographic origin of the isolates.