Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2009
Publication Date: June 1, 2009
Citation: Naegele, R.P., Hanson, L.E., McGrath, J.M. 2009. Pre-emergence Damping Off of Beta vulgaris by Rhizopus stolonifer. American Phytopathological Society Annual Meeting. 99:S92. Technical Abstract: Rhizopus stolonifer (Rs), a cool temperature zygomycete that can cause a post-harvest rot on sugarbeet (Beta vulgaris), also causes pre-emergence damping off in other crops. We are interested in its potential pre-emergence damping off activity in sugarbeet. Sugarbeets are quite susceptible to seedling diseases during germination. Germination averages 60% in Michigan fields, ranging from 0 to 100%. Lower emergence often occurs in cool, water-saturated soils. Current practices do not include management for zygomycetes and there are no known sources of genetic resistance in seedlings. This study investigated the effect of Rs on beet germination and emergence. Germination of seeds on plates and in liquid media containing spore cultures of either Rs or Phoma (used as a positive control) or a negative media control was compared after 3 and 4 days, respectively. Results indicated that Rs spores consistently reduced or inhibited germination compared to controls. In the greenhouse, surface disinfested seeds were planted and inoculated with either sterile millet or Rs infested millet. Two germplasms were used-SP6822, a putative susceptible, and EL51, a possible resistant. Germinated seedlings were counted ca. every 2 days for four weeks. Seedlings were surface disinfested for fungal isolation to confirm the presence of inoculates. Rhizopus caused an average reduction in germination of 40%, and varietal differences were observed.