Characterization of Aphanomyces euteiches Isolates Recovered from Alfalfa in Wisconsin

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Abstract
Aphanomyces-like fungal isolates recovered from alfalfa seedlings (alfalfa isolates) were morphologically similar to isolates of A. euteiches recovered from pea and green bean but were distinctly different from A. cochlioides. All alfalfa isolates were highly pathogenic on alfalfa, and one isolate was statistically more pathogenic to pea than other alfalfa isolates. All alfalfa isolates caused essentially no symptoms on hypocotyls and a low level of disease on roots of green bean. Green bean, lima bean, soybean, table beet, radish, oat, and tomato were determined to be nonhosts to alfalfa isolates of A. euteiches. Sweet clover was moderately susceptible, red clover and white clover expressed low susceptibility, and birdsfoot trefoil was highly resistant to A. euteiches. All alfalfa isolates but one grew slower than pea and bean isolates when incubated at 16-28.degree. C. However growth of alfalfa isolates, like that of pea isolates, was good at 32.degree. C compared with poor growth by bean isolates at 32.degree. C.