Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/1998
Publication Date: N/A
Technical Abstract: Twenty-three isolates of Sclerotinia sclerotiorum collected from Canada, Switzerland and US from nine hosts were evaluated for their aggressiveness on 10- to 14-day-old susceptible and partially resistant soybean seedlings. Seedlings were inoculated by placing 3-mm diameter hyphal plugs on one cotyledon per plant 5 to 7 mm away from the stem. Plants were lightly misted, covered with a plastic dome, incubated in the dark for 48 hr at 20 to 25 C. Number of dead plants over time was recorded and used to calculate area under the disease progress curve. Isolates were grouped into five different aggressiveness levels. Seventy-eight ancestor lines of modern US cultivars, 98 Asian cultivars and 110 plant introductions (PI) other than ancestor lines or Asian cultivars were evaluated using one isolate. Mandarim (Ottawa), Maple Presto, PI 248509B, PI 384942, PI 423893, PI 503336, PI 504497, PI 507327, PI 578496, PI 592949, PI 592953 and PI 594286 were the most resistant. Variation in aggressiveness of the pathogen may be significant in soybean evaluation to Sclerotinia stem rot.