DIFFERENTIAL INTERACTION OF MYCOSPHAERELLA-BRASSICICOLA AND BRASSICA CULTIVARS

Isolates of Mycosphaerella brassicicola, originating from various loca tions in Europe, differed in their virulence on a differential set of brassica cultivars, as measured by the number of lesions per leaf. Hyp ersensitivity and significant cultivar-isolate effects were observed, indicating a differential host-pathogen interaction. Although expressi on of resistance depends on plant development, the differential host-p athogen interaction was found in all plant stages tested. This is the first report on the existence of physiological specialization of M. br assicicola.