Seed and Plant Improvement Institute, Karaj, Iran.
Spot blotch caused by Bipolaris sorokiniana is a serious disease of barley in western Canada. It has become the predominant barley leaf spot disease in the province of Manitoba, Canada, since 2001. A new pathotype of B. sorokiniana with virulence on seedlings of ‘resistant’ six-rowed barley cultivars grown in Manitoba was recently identified. To determine the adult plant infection response of barley genotypes to this newly identified pathotype and to assess the extent of the damage and grain yield loss the new pathotype can cause in barley genotypes, a field trial was conducted on six barley genotypes that were inoculated with a high virulence (HV) isolate representative of the newly identified pathotype (WRS 1986) and a low virulence (LV) isolate (WRS 1949) of the pathotype. The mean infection responses of the adult barley plants inoculated with the HV isolate were generally higher than those induced by the LV isolate. Average grain yield losses caused by the HV and LV isolates were 11% and 6%, respectively. Barley line TR 251 and cultivar Stander sustained lower reductions in yield than other cultivars when inoculated with the newly emerged B. sorokiniana isolate, indicating they may possess higher levels of adult plant