Relationship between wheat rust resistance genes Yr1 and Sr48 and a microsatellite marker




A recombinant inbred line population derived from a cross between the winter wheat cultivars Arina and Forno was used to study the genetic relationship between genes Yr1 and SrAn1 in chromosome 2AL. Yr1 from Forno showed repulsion linkage (16·5 cM) with SrAn1 carried by Arina and was proximal to SrAn1. Based on the chromosomal location of SrAn1 with respect to Yr1 and its ineffectiveness against the Australian Puccinia graminis f. sp. tritici pathotype 34-1,2,7 + Sr38, it was concluded that SrAn1 is distinct from Sr21 and was designated as Sr48. An attempt was made to map more markers in the distal region of chromosome 2AL in order to determine the precise location of Sr48. Unfortunately none of the markers tested mapped between Yr1 and Sr48, with the latter being the most distal locus. However, close linkage was identified between Yr1 and the PCR-based molecular marker stm673acag. Genotyping with stm673acag amplified a 120-bp fragment in eight of nine genotypes carrying Yr1. Avocet S was the only line tested without Yr1 that also amplified the 120-bp product. A 124-bp product was amplified in 40 Australian wheat cultivars known to lack Yr1. These results suggest that stm673acag could be used for marker assisted selection of Yr1. Genotypes carrying both Yr1 and Sr48 were identified.