Genetics of Resistance to Stagonospora Nodorum Blotch of Hexaploid Wheat

The genetic control of resistance to Stagonospora nodorum blotch (SNB), caused by Stagonospora nodorum (Berk.) E. Castell. and E.G. Germano, an important foliar and head disease of wheat (Triticum aestivum L.) in many parts of the world, was investigated in five hexaploid winter wheat and one hexaploid spring wheat genotypes. F1 plant reaction and segregation data for resistance to a single Saskatchewan isolate of S. nodorum from various combinations of F2, random inbred line and doubled haploid (DH) populations of each resistant × susceptible cross indicated that single recessive genes controlled resistance in winter wheat genotypes ‘Red Chief’, ‘Hadden’, ‘Missouri Queen’, ‘Coker 76‐35’ and 81IWWMN 2095, and in spring wheat line 86ISMN 2137. All disease tests were performed on plants at the three‐leaf stage under controlled environmental conditions. Tests of F1, F2, F2:3, and DH populations from resistant × resistant crosses indicated that these six genotypes carried the same gene. The chromosomal location of this gene was determined by cytogenetic analysis with ‘Chinese Spring’ monosomic and ditelosomic lines. Tests of F1 and F2 plants from crosses between Red Chief and Chinese Spring monosomic and ditelosomic lines indicated that the gene shared by these hexaploid wheat genotypes is located on the long arm of chromosome 3A.