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Rhizosphere Effects of Pea Seed Treatment With Penicillium oxalicum. Carol E. Windels, Scientist, Department of Plant Pathology, University of Minnesota, St. Paul 55108; Thor Kommedahl, professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Phytopathology 72:190-194. Accepted for publication 15 May 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-190.

When Penicillium oxalicum-treated seeds of five pea cultivars were planted in the field in 2 yr, a greater population density of P. oxalicum and other Penicillium spp. was isolated from the rhizosphere of plants grown from P. oxalicum-treated seeds than from the rhizospheres of plants grown from captan or untreated seeds of all cultivars; these fungi accounted for a significantly greater population of total fungi for all cultivars. Seed treatment had no effect on population densities of Fusarium spp. or bacteria (including actinomycetes). Numbers of rhizosphere colonies of P. oxalicum increased at 3, 7, and 10 days after the planting of treated seeds. P. oxalicum was most frequently recovered from the proximal 2.5 cm of taproot and from the secondary roots originating from this region and less frequently from distal portions of roots. Thus, application of P. oxalicum to seeds resulted in its recovery and in greater population densities of Penicillium spp., but this treatment did not affect other microorganisms in the rhizosphere.

Additional keywords: biological control.