A Correlation of Interspecific Fertility and Conidial Morphology in Species of Helminthosporium Exhibiting Bipolar Germination

SUMMARYOf 8124 attempted interspecific crosses between 174 isolates of 16 species of Helminthosporium exhibiting bipolar germination, 47 produced viable ascospores and 24 produced sterile asci. The 16 species were placed into 5 morphology classes, based on relative shape and size of conidia. Forty-six of 2707 attempted crosses between species with similar conidial morphology were fertile, while 25 of 5417 crosses between species with different morphology were fertile. Although species in the Fungi Imperfecti are considered to be classified without “natural” criteria and merely as a matter of convenience, the frequency of cross fertility between species with a similar or different conidial morphology indicates that genetic similarities exist between related conidial forms.