Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Reduction Of A Triticum monococcum Chromosome Segment Carrying The Softness Genes Pina And Pinb Translocated To Bread Wheat

Marcos Bonafede^1,3 , Lingrang Kong² , Gabriela Tranquilli³ , Herbert Ohm² , Jorge Dubcovsky¹

¹  Department of Plant Sciences University of California at Davis Davis, CA 95616 USA

²  Department of Agronomy Purdue University 915 W. State St. West Lafayette, IN 47907-2054 USA

³  Instituto de Recursos Biologicos INTA Castelar (1712) Villa Udaondo, Buenos Aires Argentina

Endosperm texture, i.e. the hardness or softness of the grain, is an important trait because it determines many end-use properties of wheat. Endosperm texture is controlled primarily by the puroindoline genes (Pina and Pinb) at the Hardness (Ha) locus. In hexaploid wheat these genes are present on the short arm of chromosome 5D but are deleted on chromosomes 5A and 5B. The introgression of functional Pin genes from diploid wheat Triticum monococcum L. chromosome 5A^m into hexaploid wheat resulted in softer grains, suggesting that this translocation might be useful for soft wheat breeders. However, the translocated segment includes a large portion of the 5A^m short arm and may carry detrimental genes for agronomic performance. Since the T. monococcum chromosomes do not recombine well with the bread wheat chromosomes, the ph1B mutation was used to induce homoeologous recombination. Molecular markers were used to select plants heterozygous for the translocation and homozygous for the ph1B deletion. A total of 210 seeds were produced by backcrossing these plants to Chinese Spring. These lines were screened using STS markers for the BGGP gene (distal to the Pin genes) and the BQ168958 EST (proximal to Pin genes), and two SSR markers (Xgwm293 and Xgwm205). A total of 43 lines were identified with recombination events between XBQ168958 and Pin, carrying shorter 5A^m segments. An additional population of 140 F2 is being developed in addition to new markers to further reduce the length of the 5A^m segment.