Submitted to: Crop Science
Publication Type: Germplasm Release
Publication Acceptance Date: 8/31/1999
Publication Date: N/A
Interpretive Summary: Documentation of germplasm development for registration by Crop Science. Germplasm developed by solely by University of California scientists; ARS scientist provided some expertise with screening of materials for greenbug resistance. No new ARS-developed information is reported.
Technical Abstract: Interstitial translocation lines T7AS-7S#1-7AS.7AL and T7AS.7AL-7S#1L-7AL were developed from a T. speltoides (Tausch) Gren. chromosome 7S#1 originally transferred to bread wheat by irradiating hybrid seed (CI15092/ T. speltoides//'Fletcher'/3/5*'Centruk') with fast neutrons. Interstitial segments of chromosome 7S#1 were transferred to chromosome 7A of hexaploid wheat using the ph1b mutation that promotes homeologous recombination. Sears' strategy was followed to reduce length of alien chromosome segments. Interstitial translocations were backcrossed 3 times into hard white spring variety Pavon, and plants homozygous for the interstitial translocation were selected by C-banding. Translocations were characterized using molecular markers. The short arm translocation line T7AS-7S#1-7AS.7AL carries a resistance gene for leaf rust, temporarily designated LrS7. This gene confers resistance to 9 leaf rust races virulent on resistance genes Lr1 and Lr10 present in the recurrent variety Pavon. The T. speltoides segment in this translocation is located 2-10 cM from the centromere and is 20-30 cM long. The long arm translocation line T7AS.7AL-7S#1L-7AL carries gene Gb5 that confers resistance to greenbug biotypes C, E, I, and K, but not biotypes B, F, G, H. This gene is located on an interstitial T. speltoides chromosome segment 40-50 cM long located 18-22 cM from the centromere of chromosome 7AL. The segments of T. speltoides chromosome 7S#1 present in both translocation lines do not recombine with wheat chromosome 7A in the presence of the wild-type Ph1 locus and will be transmitted as a single locus. Though these translocation lines may be useful in breeding, no information is available on putative yield penalties associated to other genes in the interstitial T. speltoides chromosome 7S#1 segments.