Common and durum wheat, oats, wild oats, barley, rye, andTriticalewere moderately to highly susceptible to a non-celery-infecting isolate of the aster yellows pathogen (AY) obtained from naturally infected barley in Manitoba in 1966. The isolate produced distinctive symptoms in aster and, on the basis of these symptoms and differential transmission to several hosts, is considered to be different from previously described strains of AY. The susceptibility ofTriticaleand wild oats appears to be a new record, that of rye and the high susceptibility of oats and some common wheats, new for North America. The high susceptibility of some of these crops to AY appears to be of considerable significance in the spread of the disease.
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