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Reference Report for SoyBase10199530938
Title:Differential root resistance to Phytophthora megasperma f. sp. glycinea races in four soybean (Glycine max (L.) Merr.) varieties.
Authors:Thomison, P.R., Thomas, C.A., Kenworthy, W.J.
Source:Plant Variet. Seeds 1993, 6(2):93-96
Abstract:Differential reactions among certain soyabean (Glycine max (L.) Merr.) varieties previously characterized as tolerant of Phytophthora megasperma f. sp. glycinea Kuan and Erwin (Pmg) may be due to undescribed race-specific root resistance genes. The objective of this study was to compare reactions of the varieties Williams, Ripley and Emerald with those of the variety CNS containing the RPs-2 gene which confers root resistance to certain races of Ping. An inoculum-layer procedure was used in the greenhouse to determine reactions of the varieties to Races 1, 7 and 10. Seeds were planted 2.5 cm above an inoculum layer of lima bean agar culture. Seedling survival and seedling growth were recorded 14 days after planting as a percentage of the controls. Ratings of seedling survival and seedling growth appeared comparable in distinguishing root rot reactions. Ripley exhibited root resistance to Race 1 but showed little or no resistance to Races 7 and 10. Emerald exhibited high levels of seedling survival and seedling growth with Races 1, 7 and 10, while CNS showed similar levels of seedling survival and growth with Races 1 and 10. The highly resistant reactions of Emerald to Races 1, 7 and 10 suggest that Emerald may possess either Rps-2 and an additional gene which confers resistance to Race 7, or a gene or genes other than Rps-2 which condition resistance to all three races. The existence and characterization of additional root resistance in soyabean will provide growers with more options in the genetic control of phytophthora rot






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