Fifty isolates ofAscochyta imperfectafrom alfalfa seed grown in Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia produced varying degrees of infection on excised leaves ofMedicago falcata, Medicago sativa(three strains),Melilotus alba, Melilotus officinalis, Trifolium pratense, Lotus corniculatus, Pisum sativum, andVicia faba. Ftests from analyses of variance of disease ratings showed that the differences in susceptibility between hosts and between strains ofMedicagowere highly significant. Among the 10 hosts and within the strains ofMedicago, the interaction isolates times; hosts was highly significant. Thus, specificity among the isolates was clearly demonstrated. This is interpreted to mean that parasitic strains existed among the 50 isolates.A. imperfectawas isolated from 50 to 70 of the seed samples from each province. The heaviest infestation was on seed from Manitoba, where the weather at harvest time was wet and where the crop overwintered in the field.
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