Development of PCR markers for the wheat leaf rust resistance gene Lr47

Abstract

The leaf rust resistance gene Lr47 confers resistance to a wide spectrum of leaf rust strains. This gene was recently transferred from chromosome 7 S of Triticum speltoides to chromosome 7 A of hexaploid wheat Triticum aestivum. To facilitate the transfer of Lr47 to commercial varieties, the completely linked restriction fragment length polymorphism (RFLP) locus Xabc465 was converted into a PCR-based marker. Barley clone ABC465 is orthologous to the type-I wheat sucrose synthase gene and primers were designed for the conserved regions between the two sequences. These conserved primers were used to amplify, clone and sequence different alleles from T. speltoides and T. aestivum. This sequence information was then used to identify the T. speltoides sequence, detect allele-specific mutations, and design specific primers. Cosegregation of the PCR product of these primers and the T. speltoides chromosome segment was confirmed in four backcross-populations. To complement this dominant marker, a cleavage amplified polymorphic sequence (CAPS) was developed for the 7 A allele of Xabc465. This CAPS marker is useful to select homozygous Lr47 plants from F 2 or backcross-F 2 segregating populations, and in combination with the T. speltoides-specific primers is expected to facilitate the deployment of Lr47 in new bread wheat varieties.

Identification of microsatellites linked to Lr47

“…recombination between 7A and 7S chromosomes is prevented in presence of the Ph1 gene (Helguera et al 2000). Similar data was obtained from microsatellites wmc 168,Barc 174,wmc 497,Barc 154. The only marker that showed clear polymorphisms between Pavon and Pavon-Lr47 was gwm 60 (lane 11 and lanes 8-10, respectively in Figure 2), suggesting that it maps into the 7AS-7S#1S-7AS.7AL translocation.…”

“…RFLP markers are expensive and time consuming, therefore PCR based markers are an attractive alternative for breeding programs. Unfortunately, only PCR markers derived from the RFLP ABC465 (maps close to the last part of the 7AS-7S#1S-7AS.7AL translocation, close to the centromere) are available (Helguera et al 2000). …”

“…Each cultivar/breeding line was crossed with Pavon-Lr47 (donor of the 7AS-7S#1S-7AS.7AL T. speltoides translocation) and the nine F 1 s were backcrossed with the respective parents. In each of the 4 BC generations (or 6 in Kern, Yecora Rojo, Express, UC1037, UC1041 and RS15) two individuals heterozygous for the 7AS-7S#1S-7AS.7AL translocation were selected by marker assisted selection using Lr47 specific markers according to Helguera et al (2000). Finally, BC 4 (or BC 6 ) plants heterozygous for 7AS-7S#1S-7AS.7AL translocation were self-pollinated and homozygous 7AS-7S#1S-7AS.7AL plants were selected from BC 4 F 2 (or BC 6 F 2 ) using codominat Lr47 markers (Helguera et al 2000).…”

“…In each of the 4 BC generations (or 6 in Kern, Yecora Rojo, Express, UC1037, UC1041 and RS15) two individuals heterozygous for the 7AS-7S#1S-7AS.7AL translocation were selected by marker assisted selection using Lr47 specific markers according to Helguera et al (2000). Finally, BC 4 (or BC 6 ) plants heterozygous for 7AS-7S#1S-7AS.7AL translocation were self-pollinated and homozygous 7AS-7S#1S-7AS.7AL plants were selected from BC 4 F 2 (or BC 6 F 2 ) using codominat Lr47 markers (Helguera et al 2000). These selected BC 4 F 2 plants are expected to be 96.8% (or more than 99% in BC 6 F 2 ) identical to the recurrent parent and homozygous for the Lr47 gene.…”

Genetic analysis of rust resistance genes in global wheat cultivars: an overview

“…The resistance gene Sr35 was originally [88] transferred from Triticum monococcum to hexaploid wheat [36] and is effective against the TTKSK (Ug99) race of P. graminis f. sp. tritici [64] and its variants. This gene was mapped to the long arm of chromosome 3AL.…”