Location: Hard Winter Wheat Genetics Research Unit
2013 Annual Report
In order to produce commercially competitive varieties of the future, new stem rust resistance genes must be incorporated into a forward breeding program. In addition, a backcross breeding program is required both for parent-building and as a hedge if commercially acceptable resistant varieties are needed in the short term. Rapid breeding methods, such as doubled haploids, will be needed to achieve results as quickly as possible.
Phenotypic selection for resistance using common North American races will be difficult in most backgrounds due to the high frequency of endemic stem rust resistance genes. Therefore, marker-assisted selection for new resistance genes will be necessary. Molecular markers are available or under development for virtually all new sources of stem rust resistance. Marker genotypes will be generated locally or in a high throughput facility at the USDA-ARS Regional Small Grains Genotyping Laboratory in Manhattan, KS. Resistance of advanced lines against African races of stem rust will be confirmed by field testing at cooperative research facilities in Kenya or at the USDA-ARS Cereal Disease Laboratory. Testing for agronomic traits, yield, and quality will be performed as usual by the breeding program.
Lyman, a variety released from South Dakota State University (SDSU) in 2008, which has good resistance to the important diseases encountered in South Dakota and the region, and a breeding line from SDSU (SD5085) have been sent to a USDA-ARS lab in Fargo, ND. The purpose was to have them hybridize these two genotypes with several of their genetic stocks to transfer stem rust resistance genes to adapted South Dakota genotypes. Genes to be transferred include; Sr2, Sr25, Sr26, Sr36, Sr22, Sr35, and Sr40. Some material resulting from a hybridizations between cultivars ‘Lyman’ and ‘Wheatear’ (source of Sr25), and ‘Lyman’ and WA-1 (source of Sr26) are at the BC2F2 stage.
The SDSU Winter Wheat Breeding Program advanced breeding lines from AYT and CPT nurseries, which were screened in the greenhouse for resistance to US local races of stem rust. In addition, those lines have routinely been sent to Kenya for screening for resistance to endemic races of Ug99.
The SDSU advanced breeding lines have also been evaluated through the Northern Regional Performance Nursery (NRPN) for stem rust seedling resistance for common US races and Ug99 races (TTKSK, TTKST, and TTTSK). Most of the SDSU breeding lines included in the trial in 2013 have shown some levels of resistance to Ug99 races.
We are expecting to receive seed from hybridizations made by the USDA-ARS Fargo lab in the coming month. Some of this material will be used to pyramid several sources of resistance to Ug99 into genotypes adapted to South Dakota and the region.
In addition, we are expecting to receive some BC1F2:3 lines in a Duster background containing Sr22, Sr26, Sr35 and Lr34 from a USDA-ARS lab in Manhattan, KS. This material will be hybridized with selected, elite promising SDSU advanced breeding lines.
In coordination with the USDA Genotyping Lab in Manhattan, KS, as appropriate and necessary, germplasm will be sent for stem rust gene validation.
As in previous years, SDSU advanced breeding lines from Advanced Yield Trial (AYT) and Crop Performance Trial (CPT) nurseries will be screened in the greenhouse for resistance to regional US races of stem rust. Elite SDSU breeding lines will be included in the NRPN, and within the parameters of this regional trial, they will be screened for stem rust resistance at the seedling stage and for resistance to Ug99 as part of a collaborative nursery grown in Kenya.
The overall goal of SDSU breeding program is to develop and release new varieties with excellent agronomic characteristics, resistance to diseases prevalent in South Dakota and the region, good end-use quality and winter hardiness. As genes for resistance to Ug99 are pyramided into SDSU advanced breeding lines, all lines will undergo genotyping and phenotyping to validate performance and response to various races of Ug99.