STUDIES ON LEPTOSPHAERIA AVENARIA f. sp. TRITICEA ON CEREALS AND GRASSES

Abstract

Cultures were established from pycnidiospores assignable to Septoria avenae Frank collected on wheat, oats, barley, rye, and grasses in Canada. Those cultures that were nonpathogenic on oats produced, in most cases, perithecia and viable ascospores of Leptosphaeria avenaria Weber, as well as the asexual spores. Cultures were also established from asci and ascospores assignable to L. avenaria collected on wheat, oats, barley, rye, and grasses. Those that were nonpathogenic on oats produced, in most cases, pycnidiospores of S. avenae as well as the sexual spores. Many of the isolates produced slight to trace infection on the wheat variety Gaza and trace infection on barley. Oats, rye, and certain grasses were immune. It is considered that the isolates are a plurivorous group slightly pathogenic on wheat and found on the senescent parts of other cereals and grasses, and that they are best assigned to L. avenaria f. sp. triticea. No microspores were found in any of the cultures. Perithecia with viable ascospores formed in 123 cultures out of 164 established from single ascospores, some of the lines being maintained by single ascospore transfer up to five generations. This special form is therefore regarded as homothallic.