First report of Mycosphaerella graminicola, the sexual state of Septoria tritici, in Manitoba, Canada

Abstract

Mycosphaerella graminicola, the sexual state of Septoria tritici that causes speckled leaf blotch in wheat, was found in wheat stubble during the summer of 2001 in southwestern Manitoba. This is the first time that the teleomorph of the pathogen has been identified by direct observation in Canada. Ascospores isolated from pseudothecia formed similar conidial colonies on agar media as the pycnidiospores of Septoria tritici, the asexual state. Wheat plants inoculated with conidia derived from ascospore isolates developed symptoms typical of speckled leaf blotch. Single cirrhi were picked from the necrotic lesions to reisolate the pathogen. Budding conidial colonies identical to those produced by the germination of the ascospores were obtained. These aforementioned steps prove that the pseudothecia found in the wheat stubble were those of M. graminicola. Therefore, it can be assumed that M. graminicola ascospores contribute to the primary inoculum of speckled leaf blotch in Manitoba. The presence of the sexual state in Canada has been anticipated and is consistent with reports from other regions of the world.