THE INHERITANCE OF RUST RESISTANCE. III. THE INHERITANCE OF STEM RUST RESISTANCE IN NINE KENYA VARIETIES OF COMMON WHEAT

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Abstract
The inheritance of resistance to races 15B and 56 of stem rust was studied in the varieties Kenya 58, Kenya 117A, Kenya C9906, Kenya 338.AC.2.E.2, Kenya Governor, Kenya B286, Kenya 291.J.1.I.1, Kenya 321.BT.1.B.1 and Kenya 350.AD.9.C.2. The first five varieties had been studied previously and crosses involving them were not repeated. The genetic analysis of the varieties was based on diallel crosses and backcrosses to a susceptible parent, Marquis.All nine varieties proved to carry Sr7, a gene which conditions resistance to race 15B. Four varieties, Kenya 58, Kenya C9906, Kenya 291 and Kenya 350, carry the gene Sr6, which conditions a hypersensitive reaction to both race 15B and race 56. In addition, four of the varieties carry Sr9 and five carry Sr10, two genes which produce moderate resistance to race 56. Kenya 338.AC.2.E.2 carries two additional dominant, complementary genes, Sr11 and Sr12, which condition resistance to race 56.The genes, Sr9, Sr10, Sr11 and Sr12 are important modifiers of the resistance to race 15B conditioned by Sr7, with Sr9 probably having the greatest effect.