IDENTIFICATION OF THE STEM RUST RESISTANCE GENE PG9 AND ITS ASSOCIATION WITH CROWN RUST RESISTANCE AND ENDOSPERM PROTEINS IN DUMONT OAT

The Canadian oat cultivar 'Dumont' is known to have genes Pc38 and Pc3 9 for crown rust resistance and genes Pg2 and Pg13 for stem rust resis tance. When crossed to a susceptible oat line OT328,'Dumont' was shown to have an additional dominant gene for crown rust resistance, design ated PcX. Tests of segregating progeny indicated that the stem rust re sistance gene Pg9 is present and is tightly linked in coupling to PcX. The presence of Pg9 in 'Dumont' was confirmed in crosses involving th e cultivar 'Ukraine', which has Pg9 and a crown rust resistance gene t ightly linked to it. The association of rust resistance with endosperm proteins in 'Dumont' was investigated. The linkage of gene Pg13 with a 56.6-kDa polypeptide locus (map distance of 10.47 +/- 2.70 cM) was d emonstrated using sodium dodecylsulfate - polyacrylamide gel electroph oresis (SDS-PAGE). A 27.9-kDa polypeptide was shown to be associated w ith the linked PcX/Pg9 loci by SDS-PAGE but appeared to be more reliab ly separated as an avenin band, designated B-4, using acid-PAGE. Anoth er avenin band, designated B-2, also was shown to be associated with t he PcX/Pg9 loci using acid-PAGE. The loci conditioning the B-2 and B-4 bands appeared to be tightly linked or allelic and are separated from the linked PcX/Pg9 loci by a map distance of 1.03 +/- 0.36 cM. The as sociation of Pg13 with a 56.6-kDa polypeptide and the tight linkage be tween PcX/Pg9 and the B-2 (in coupling) and B-4 (in repulsion) avenin loci offer a useful tool to breeders to detect the presence of these g enes in oat breeding.