DETERMINATION OF RELATIONSHIPS IN PSEUDOCERCOSPORELLA-HERPOTRICHOIDESBY ANALYSIS OF MITOCHONDRIAL-DNA

Relatedness between isolates of Pseudocercosporella herpotrichoides, t he 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. herpot richoides, identified on the basis of cultural characteristics on PDA: fast-growing, even-edged (FE) and slow-growing, feathery or uneven-ed ged (SF). The nucleotide sequence divergence of mtDNA between these tw o groups was considerably higher than that between isolates belonging to the same taxa of fungi. Within each group, minor or no polymorphism s were observed among isolates from diverse geographical origins. An i solate of pathotype C could not be distinguished from the other FE iso lates of P. herpotrichoides. Major nucleotide sequence divergence of m tDNA was observed among isolates of both groups of P. herpotrichoides, P. anguioides and P. aestiva, indicating there are no dose relationsh ips among these species. This study suggests that isolates of P. herpo trichoides consist of two genetically distinct taxonomic groups, corre sponding to separate species.