Aphanomyces euteiches, a Novel Root Pathogen to Alfalfa in Québec. C. Richard, Agriculture Canada Research Station, Sainte-Foy, Québec G1V 2J3. A. Beghdadi, and J.-G. Martin. Agriculture Canada Research Station, Sainte-Foy, Québec G1V 2J3. Plant Dis. 75:319. Accepted for publication 14 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0319B.
In 1989, three isolates of Aphanomyces sp. were obtained by a
baiting technique from soils sampled in low areas of three fields where
poor survival of alfalfa (Medicago sativa L.) was observed. Isolates
were identified as A. euteiches Drechs. on the basis of hyphae, sporangia,
primary spores, oogonial characteristics, growth rate, and results
of pathogenicity tests with Koch's postulates on alfalfa, table beet,
radish, green bean, and pea (l). The isolates caused postemergence
damping-off, root and hypocotyl browning, chlorosis, and death of
seedlings. All three isolates were highly pathogenic to alfalfa cv. Vernal
but differed in their pathogenicity to pea, rate of growth at 32 C,
and dimension of oogonia and aplerotic zone. Two of the isolates
belong to the alfalfa group (1). This is the first report of A. euteiches
on alfalfa in the province of Quebec. Aphanomyces has been described
as a significant root pathogen of alfalfa in other areas (1).