UC Davis

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.