Disease resistance: leaf and stripe rust

Lr47

References

1.Molecular characterization of two Triticum speltoides interstitial translocations carrying leaf rust and greenbug resistance genes. Dubcovsky, J.; Lukaszewski, A. J.; Echaide, M.; Antonelli, E. F.; Porter, D. R. In: Crop Science Nov.-Dec., 1998. 38 (6): 1655-1660.

Resistance genes for leaf rust (Puccinia recondita Rob. ex Desm.) and greenbug (Schizaphis graminum Rondani) were transferred from chromosome 7S of Triticum speltoides (Tausch) Gren. to chromosome 7A of hexaploid wheat (Triticum aestivum L.) by means of the ph1b mutation that promotes homeologous recombination. The chromosome segments from T. speltoides were characterized by C-banding and restriction fragment length polymorphisms (RFLP). Since the segments of T. speltoides chromosome 7S do not recombine with wheat chromosome 7A in the presence of the wild-type Ph1 locus only one molecular marker per chromosome segment is required to monitor the introgressed genes in marker assisted selection programs. The new leaf rust resistance gene, designated Lr47, and the greenbug resistance gene Gb5 were located on interstitial chromosome segments from T. speltoides translocated to wheat chromosome arms 7AS and 7AL, respectively. Physically, both were located in the distal one third of the arms, but genetically the Lr47 segment was 2 to 10 centimorgans (cM) from the centromere and was 20 to 30 cM long; the Gb5 segment was 18 to 22 cM from the centromere and was 40 to 50 cM long.

2.Development of PCR markers for wheat leaf rust resistance gene Lr47. Helguera, M.; Khan, I. A.; Dubcovsky, J.. In: Theoretical and Applied Genetics September, 2000. 101 (4): 625-631.

The leaf rust resistance gene Lr47 confers resistance to a wide spectrum of leaf rust strains. This gene was recently transferred from chromosome 7S of Triticum speltoides to chromosome 7A 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 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 7A allele of Xabc465. This CAPS marker is useful to select homozygous Lr47 plants from F2 or backcross-F2 segregating populations, and in combination with the T. speltoides specific primers is expected to facilitate the deployment of Lr47 in new bread wheat varieties.