ISOZYME POLYMORPHISM IN PATHOTYPES OF PSEUDOCERCOSPORELLA-HERPOTRICHOIDES AND RELATED SPECIES FROM CEREALS

Isolates of Pseudocercosporella herpotrichoides, causal agent of the eyespot disease of cereals, are usually classified as W‐type or R‐type on the basis of differential pathogenicity towards wheat and rye hosts, a distinction often correlated with cultural morphology. Polyacrylamide gel electrophoresis (PAGE) of soluble proteins was used to compare 101 isolates of Pseudocercosporella spp. including both W‐types and R‐types, and the related species P. anguioides and P. aestiva. Of 16 enzyme activities detected, seven were differential for the pathotypes. Isozyme polymorphisms for five enzymes clearly differentiated W‐type from R‐type isolates, a result confirmed by pathogenicity tests. Within each pathotype, isozyme patterns were similar for isolates of diverse geographical origins, including Europe, North America, South Africa and New Zealand. Isolates of P. anguioides and P. aestiva could also be distinguished on the basis of isozyme patterns. The mechanisms maintaining these polymorphisms, and the value of PAGE for population studies of this pathogen, are discussed. Copyright © 1990, Wiley Blackwell. All rights reserved