Major and Minor Genes in Wheat for Resistance to Puccinia Striiformis and Their Responses to Temperature Changes

The wheat varieties, 'P.I. 178383' and 'Chinese 166' (Triticum aestivum), were each found to carry an incompletely dominant major gene for resistance to a single pathogenic type of Puccinia striiformis. In addition, an undetermined number of minor genes segregated in such a way that in certain combinations they conferred moderate resistance and modified the action of the major genes. The rust readings were made on seedling plants grown in strictly controlled-environment chambers that simulated natural conditions. The action of the major genes was not affected by different temperature profiles, but the minor genes gave better resistance at a higher temperature profile than at a lower temperature profile.