Monday, November 13, 2006
74-5
MARKER-ASSISTED BACKCROSS BREEDING FOR SIMULTANEOUS INTROGRESSION OF STRIPE RUST RESISTANCE GENES Yr5 AND Yr15 INTO SPRING WHEAT (Triticum aestivum L.).
Dipak Santra1, Victor DeMacon1, Kimberly Garland-Campbell2, and Kimberlee Kidwell1. (1) Dep. of Crop and Soil Sciences, 201 Johnson Hall, Washington State University, Pullman, WA 99164-6420, (2) USDA-ARS, 209 Johnson Hall WSU USDA-ARS, Box 646420, Pullman, WA 99164-6420
A common strategy for enhancing durability of resistance is to pyramid effective resistance genes into a same genetic background. Stripe rust is one of the most devastating diseases of wheat worldwide. Single, dominant genes Yr5 and Yr15, independently confer complete resistance to all stripe rust races found in North America to date. The objectives of this study were to: (1) pyramid Yr5 and Yr15 into a common genetic background via marker-assisted backcross breeding (MABB); (2) evaluate backcross-derived genotypes for stripe rust resistance in the field; and (3) confirm the presence of both genes in a single genotype through testcross analysis. Spring wheat genotypes ‘Scarlet’, ‘Zak’ and ‘WA7900’ are highly susceptible to prevalent stripe rust races in the Pacific Northwest region of the United States; therefore, these genotypes were chosen as the recurrent parents for Yr5 and Yr15 gene pyramiding efforts using Yr5/6*Avocet S and Yr5/6*Avocet S as donor parents. Following independent single gene introgression through traditional F1 hybrid development, the two F1 lines carrying each gene were intercrossed. Resulting F1F1 progeny carrying Yr5 and Yr15 were identified using flanking DNA markers associated with each gene. Repeated rounds of MABB were conducted to identify progeny carrying both Yr5 and Yr15, which were self-pollinated for advancement to the next generation. This approach was used to develop BC4F4 derivatives of Scarlet and Zak, and BC3F4 derivatives of WA7900, homozygous for both target genes. All these backcross derivatives were completely resistant to stripe rust when tested in the field in Pullman, WA in 2006. The presence of both Yr5 and Yr15 in the homozygous state was confirmed through testcross analyses. The outcome of this work demonstrated the utility of MABB for gene pyramiding in wheat, and resulted in the development of genotypes with durable stripe rust resistance that have cultivar release potential.