II.50. Work in progress.
M. S. Wolfe, R. A. Finch and R. Johnson. Plant Breeding Institute, Trumpington, Cambridge, England.
Inheritance of resistance to powdery mildew, yellow rust and brown rust in relation to morphological characters is being investigated in thirty lines originally selected for resistance to powdery mildew. Disease tests are being conducted at the seedling stage, but subsequently it is intended to investigate the inheritance of resistance in the field.
Results obtained with varieties which possess powdery mildew resistance at the mlo locus are reported elsewhere in this Newsletter. In addition, nine lines have been found which possess resistance genes at, or near, the Mla locus, nine lines have resistance conditioned by unknown dominant genes, and two lines have unidentified recessive genes for resistance.
Fourteen of the powdery mildew resistant lines are also resistant either to race 23, or to races 23 and 24 of Puccinia striiformis. The variety Cambrinus, which is resistant to race 23 but not to race 24, has a single dominant gene conditioning the resistance: two other lines have a recessive gene conditioning resistance to race 23 and, possibly, to race 24.
Eight of the original lines are resistant to brown rust. Attempts have been made to relate the inheritance of resistance to the two rust diseases but simultaneous inoculation with the two pathogens has proved troublesome.
From the combined data it is hoped to produce additional information on the mapping of disease resistance and morphological loci partly in order to correlate some of the separate pieces of information which exist in the literature, concerning the location of disease resistance genes.