RESPONSES OF BARLEY CULTIVARS AND LINES TO ISOLATES OF PYRENOPHORA-TERES

Net blotch, caused by Pyrenophora teres, is among the most damaging fo liar diseases of barley worldwide. A knowledge of the reaction of loca l cultivars, putative resistant lines, and variability in the net blot ch pathogen is necessary to develop a successful resistance breeding p rogram. Disease responses of 38 barley lines to 15 P, teres isolates w ere: studied at the seedling and adult plant stages in the glasshouse, and field responses to net blotch were evaluated at three Moroccan lo cations. No tested barley was resistant to all isolates, and resistanc e was apparently of the specific type. Pathogenic variability was grea t, as none of the 15 isolates were identical. For each isolate tested, a specific high level of resistance was found in one or more host lin es. Seedling and adults plants often differed in response to the. same isolate. Adult plant resistance was commonly observed in response to isolate I-1, and seedling resistance was more common to isolate I-14. Adult plant resistance of nine lines was undetected in seedling evalua tions using isolate I-1. The seedling glasshouse and field responses o f the barley lines varied considerably, limiting the value of seedling testing for resistance, Field reactions of resistant and moderately r esistant were consistent across the three locations for the lines Hear tland, Minn 7, CI 2333, and CI 2549. The variability observed in P. te res and failure to find lines with resistance to all isolates suggests that breeding for resistance should emphasize pyramiding of resistanc e genes.