GRASS HOSTS OF PYRENOPHORA-TRITICI-REPENTIS

Sixty-two isolates of Pyrenophora tritici-repentis were obtained from diseased leaves collected from 25 grass species. Nine species were previously unreported hosts, including Agropyron fragile subsp. sibiricum (Siberian wheatgrass), Andropogon gerardii var. paucipilus (sand bluestem), Bromus biebersteinii (meadow brome), Festuca ovina (sheep fescue), Koeleria pyramidata (June grass), Schizachyrium scoparium (little bluestem), Setaria viridis (green foxtail) Stipa comata (needle-and-thread), and Thinopyrum ponticum (tall wheatgrass). All isolate; from grass hosts produced symptoms on detached seedling leaves of wheat (Triticum aestivum) and were considered pathogenic. Significant isolate effects in all analyses were interpreted to indicate that isolates from the grass hosts differed in their ability to cause disease symptoms on wheat. A number of isolates from grass hosts were as aggressive as a wheat isolate. Cultivar effects were significant in 86% of the analyses, indicating that differences in symptom response among wheat cultivars were detected when tested with isolates from the grass hosts. However, the cultivar X isolate interaction was nonsignificant in 86% of the analyses, indicating a lack of specific interaction between isolates and cultivars.