Studies on Graminicolous Species of Phyllachora Fckl. III.. The relationship of certain Scolecospores to species of Phyllachora

Abstract

The present study and a survey of literature showed that of the various spore types associated with species of Phyllachora, scolecospores typical of the form genus Leptostromella were most common. Examination has shown that certain spore types claimed as imperfect states of Phyllachora species are actually spores of hyperparasites. Evidence that the scolecospores belong to the Phyllachora species with which they are associated has been gathered.

Studies on the development of P. parilis showed that the scolecospores associated with the perithecia of this species were genetically related to it. Attempts to germinate the scolecospores associated with three species of Phyllachora were unsuccessful. Similarly, when scolecospores 'were used as inoculum, test plants did not become infected. When ascosporic inoculum were used, however, infection occurred. Only one type of mycelium was found in each infection court, and pycnidia and perithecia developed from this in close association. Consequently, although the scolecosporous pycnidia developed prior to the perithecia, both types of fructification occurred in individual Phyllachora colonies. Within each mature colony the tissues of the pycnidia, perithecia, and clypeus became fused and were indistinguishable from one another.

The development of the pycnidium and scolecospores is described, and it is shown that a different species of Leptostromella is associated with each different Phyllachora species. The Leptostromella species can be distinguished especially by the morphology of their sporophores.

When it was shown that the morphology of the Leptostromella associated with each Phyllachora species was distinctive and constant, it was possible to assess the frequency and distribution of these associations. With some species of Phyllachora the association occurred in all specimens, while in others it was not as frequent. Always, however, the distribution of the association was as widespread as the species of Phyllachora concerned.

It was noted that hyperparasites were able to parasitize the Leptostromella states as readily as the ascal states of various species of Phyllachora. The function of the scolecospores is not known, but it is suggested that they may be spermatia.