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 Pc39 for crown rust resistance and genes Pg2 and Pg13 for stem rust resistance. When crossed to a susceptible oat line OT328, 'Dumont' was shown to have an additional dominant gene for crown rust resistance, designated PcX. Tests of segregating progeny indicated that the stem rust resistance gene Pg9 is present and is tightly linked in coupling to PcX. The presence of Pg9 in 'Dumont' was confirmed in crosses involving the cultivar 'Ukraine', which has Pg9 and a crown rust resistance gene tightly 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 demonstrated using sodium dodecylsulfate – polyacrylamide gel electrophoresis (SDS–PAGE). A 27.9-kDa polypeptide was shown to be associated with the linked PcX/Pg9 loci by SDS–PAGE but appeared to be more reliably separated as an avenin band, designated B4, using acid–PAGE. Another avenin band, designated B2, also was shown to be associated with the PcX/Pg9 loci using acid–PAGE. The loci conditioning the B2 and B4 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 association of Pg13 with a 56.6-kDa polypeptide and the tight linkage between PcX/Pg9 and the B2 (in coupling) and B4 (in repulsion) avenin loci offer a useful tool to breeders to detect the presence of these genes in oat breeding.Key words: avenins, gel electrophoresis, molecular markers.