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Plant Loss Response of Soybean Cultivars to Phytophthora megasperma f. sp. glycinea Under Field Conditions. R. I. Buzzell, Breeder, Agriculture Canada, Research Station, Harrow, Ontario N0R 1G0. T. R. Anderson, Plant Pathologist, Agriculture Canada, Research Station, Harrow, Ontario N0R 1G0. Plant Dis. 66:1146-1148. Accepted for publication 2 March 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-1146.

Soybean cultivars and lines were evaluated on Brookston clay during 19771980 for plant loss caused by Phytophthora megasperma f. sp. glycinea. Races 3, 7, and 9 of the pathogen were predominant in the soil. Hypocotyl inoculations with races 1, 3, 4, 7, and 9 indicated that some cultivars and lines carried race-specific resistance that resulted in low plant loss. Other variability in plant loss among entries was ascribed to tolerance. There was no significant cultivar × year interaction in 2-yr and 4-yr analyses; broad-sense heritabilities from these analyses were 93 and 96%. Selection for tolerance based on low plant loss, followed by backcrossing to include race-specific resistance, should provide effective, long-term disease control.