SYSTEMATICS OF ITERSONILIA - A COMPARATIVE PHENETIC STUDY

A comparative study of Itersonilia included comparative morphology, nutritional physiology, septal ultrastructure, karyology and mating of yeast phases. Strains isolated from parsnip produce more chlamydospores than those from other sources, which frequently do not form chlamydospores at all. However, integrading forms do occur. No species-specific differences are found in the nutritional physiology. Monokaryotic yeast phases sometimes differ physiologically from parental strains, which are mostly dikaryotic. Yeast phases sometimes revert to monokaryotic hyphal phases with pseudoclamps. No karyogamy has been observed. The mating system seems to be tetrapolar. The presence of a relatively simple dolipore without parenthesomes points to a relationship with Tremellales. Because of 'interspecific' mating reactions the existence of separate species, I. perplexans, I. pyriformans and I. pastinacae is strongly questioned.