|Helguera, M - UNIV CALIF - DAVIS|
|Khan, I - UNIV CALIF - DAVIS|
|Lijavetzki, D - UNIV CALIF - DAVIS|
|Zhong Qi, L - UNIV CALIF - DAVIS|
|Dubcovsky, J - UNIV CALIF - DAVIS|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 24, 2003
Publication Date: September 1, 2003
Citation: Helguera, M., Khan, I.A., Kolmer, J.A., Lijavetzki, D., Zhong QI, L., Dubcovsky, J. 2003. PCR assays for the L37-YR17-SR38 cluster of rust resistance genes and their use to develop isogenic hard red spring wheat lines. Crop Science. 43:1839-1847. Interpretive Summary: Three different types of fungi, known as rusts, can attack wheat. Stripe rust, leaf rust, and stem rust are all important diseases of wheat in the United States. Genes for rust resistance in wheat can be used to limit yield losses in wheat due to the three rust diseases. Biotechnology methods are used to develop molecular markers for rust resistance genes in wheat. Molecular markers can quickly detect the presence of rust resistance genes in wheat without needing to grow adult wheat plants and test the plants for resistance to rust. In this study a molecular marker was developed to detect the stripe rust resistance gene Yr17, the leaf rust resistance gene Lr37, and the stem rust resistance gene Sr38, which are all located on the same chromosome region in wheat. The molecular marker was used to add rust resistance genes to four different spring wheats. The molecular marker can be used by wheat breeders to more quickly incorporate the three rust resistance genes into their breeding materials.
Technical Abstract: Rust resistance genes Lr37, Sr38, and Yr17 are located within a segment of Triticum ventricosum chromosome 2NS translocated to the short arm of bread wheat chromosome 2AS. Characterization of this chromosome segment with RFLP markers indicated that the translocation includes the distal 5-10 cM of chromosome 2NS. Three different PCR assays were developed from RFLP marker cMWG682 to facilitate the transfer of this cluster of rust resistance genes to commercial wheat cultivars. First, Eco RI digested genomic DNA was purified from agarose gels from the regions corresponding to the approximate location of A, B, D, and N-genome RFLP bands. Primers based on conserved regions of cMWG682 sequence were used to amplify, clone, and sequence different copies from each genome. Sequence information was used to design N genome specific primers. The 2N fragment amplified by PCR primers co-segregated with the presence of the RFLP-2N band in all backcross populations. A cleavage amplification polymorphism (CAPS) was used to develop a marker for the 2AS allele. This marker was used to differentiate homozygous and heterozygous plants carrying the 2NS translocation in the final cycle of backcross introgression or in screenings of homozygous plants in F2 populations. Finally, a third PCR assay was developed using TaqMan ® technology to accelerate selection procedures in breeding programs that have access to real time PCR equipment. These molecular markers were used to develop four hard red spring isogenic lines homozygous for the 2NS chromosome segment. These isogenic lines provide a sensitive tool to test the effects of the 2NS translocation on quality and agronomic performance.