Chromosomal variability in Phyllactinia (Erysiphaceae)

Cytological studies on Phyllactinia show both inter- and intra-specific polyploidy. Changes of chromosome number may or may not result in morphological changes which lead to the formation of new species. These intra-specific variants have been termed chromosome races; P. guttata has five while P. dalbergiae has two. The importance of these variants in relation to pathogenicity, host range, species delimitation and the basic chromosome number in the genus Phyllactinia are discussed.