Chromosomal location of an uncharacterised stripe rust resistance gene in wheat

A recent introduction of Puccinia striiformis f. sp. tritici (Pst) pathotype 134 E16A+ in Western Australia differed from existing pathotypes in its virulence for stripe rust resistance genes Yr8 and Yr9, and avirulence for Yr3, Yr4, Yr34 and some uncharacterized sources of resistance. The Australian wheat cultivar Rubric exhibited a very low seedling stripe rust response when tested against the Pst pathotype 134 E16A+. Genetic analysis of a Rubric/Avocet ‘S’ F3 population indicated monogenic inheritance of resistance. The resistance gene was tentatively designated YrRub. Bulked segregant analysis using multiplex-ready PCR technology placed YrRub distal to the microsatellite marker barc75 in chromosome 3BS. Follow up studies mapped SSR marker cfb3530 between YrRub (2.9 ± 1.3 cM) and barc75 (2.4 ± 1.2 cM). Genotypes Bolac, EMU ‘S’, Nesser, Hybrid 46 (Yr4) and Avalon (Yr4) amplified the YrRub-linked barc75 and cfb3530 alleles. The amplification of PCR products similar to that of Rubric in Yr4-carrying cultivars Hybrid 46 and Avalon suggested that YrRub was most likely to be Yr4. Due to unavailability of genotypes carrying Yr4 singly, test of allelism was not possible. Thirty-eight Australian wheat cultivars known to lack YrRub, an advanced breeding line WAWHT2046 (Yr34) and Vilmorin 23 (Yr3) amplified PCR products different from that of Rubric at the barc75 and cfb3530 marker loci. The amplification of non-Rubric alleles at the marker barc75 and cfb3530 loci among a set of diverse wheat genotypes demonstrated that these markers could be used for marker assisted selection of YrRub in combination with other molecularly tagged seedling and adult plant stripe rust resistance genes in wheat breeding programs.