Determination of relationships in Pseudocercosporella herpotrichoides by analysis of mitochondrial DNA

Abstract

Relatedness between isolates of Pseudocercosporella herpotrichoides, the causal fungus of eyespot disease of cereals, was investigated by a quantitative analysis of restriction fragment length polymorphisms of mitochondrial DNAs. Restriction patterns of mtDNA for all nine enzymes used in this study were different between the two groups of P. herpotrichoides, identified on the basis of cultural characteristics on PDA: fast-growing, even-edged (FE) and slow-growing, feathery or uneven-edged (SF). The nucleotide sequence divergence of mtDNA between these two groups was considerably higher than that between isolates belonging to the same taxa of fungi. Within each group, minor or no polymorphisms were observed among isolates from diverse geographical origins. An isolate of pathotype C could not be distinguished from the other FE isolates of P. herpotrichoides. Major nucleotide sequence divergence of mtDNA was observed among isolates of both groups of P. herpotrichoides, P. anguioides and P. aestiva, indicating there are no close relationships among these species. This study suggests that isolates of P. herpotrichoides consist of two genetically distinct taxonomic groups, corresponding to separate species.