STEM AND CROWN RUST RESISTANCE IN THE WISCONSIN OAT SELECTION X1588-2

The Wisconsin oat (Avena sativa L.) selection X1588-2 has reacted either with mesothetic (moderately resistant) or 0;1 (highly resistant) infection types to races of Puccinia graminis Pers. f. sp. avenae Eriks. and E. Hem. (stem rust). This selection also is resistant to some pathotypes of P. coronata Cords f. sp. avenae Eriks. (crown rust). The objectives of this study were to identify the genes in X1588-2 responsible for the rust resistance and to determine the usefulness of this line as a source of resistance in oat breeding. Tests with 45 races of P.g. avenae showed that X1588-2 was highly resistant to races that were avirulent to genes Pg3 and/or Pg4 and was moderately resistant to all other races. These results and the pedigree of X1588-2 indicated the presence of stem rust resistance genes Pg3, Pg4, and Pg10 is X1588-2. The presence of these genes was further indicated in tests of seedlings of segregating BC1F1 and BC1F2 populations from a cross of X1588-2 with the susceptible cultivar Makuru. Resistance to crown rust in X-1588-2 was conferred by a gene designated as Pc95. The resistance conferred by Pc95, however, was not effective against a sufficient range of pathotypes of P. coronata to be a useful source of resistance. Genes Pg3 and Pg4 are ineffective against current North American populations of P.g. avenae. Gene Pg10, however, appears to confer a moderate but very broad range of resistance and may be a useful source of resistance in oat breeding.