Studies on Oat-Attacking and Wheat-Attacking Isolates of Ophiobolus Graminis in Australia

Abstract

Isolates of an oat-attacking strain of OphioboIu8 gram~nt8 from Western Australia were differentiated from other isolates by comprehensive pathogenicity tests. Differential criteria for the two recognized varieties of O. gramini8 indicated that the Western Australian oat isolates were similar to var. avenae; South Australian isolates from oats were pathogenically similar to the type variety although some resembled var. avenae in their tolerance of oat extract. Pathogenicity on oats was the most reliable differential criterion and size of asci and ascospores the least; ascospore size was influenced by substrate, being generally greater in culture than on host tissue. Nuclear distribution in mycelia of wheat- and oat-attacking strains was similar but attempts to induce hyphal anastomosis between the two were unsuccessful.