THE INCURSION OF NEW WHEAT STEM RUST RACES INTO THE UNITED STATES: PREPARATION THROUGH RESEARCH, EDUCATION AND EXTENSION
2012 Annual Report
1a.Objectives (from AD-416):
The primary objective is to help facilitate enhancement of U.S. wheat cultivars by supporting movement of genes with effective stem rust resistance to new Pgt races into elite wheat germplasm.
1b.Approach (from AD-416):
Marker assisted selection will be used to enhance the movement of effective stem rust resistance genes into advanced breeding lines of wheat.
The LSU AgCenter wheat breeding program continued efforts to increase the frequency of genes in the breeding program that are effective against races of wheat stem rust (Puccinia graminis tritici - Pgt) described as Ug99 including TTKST, TTKSK, and TTTSK. LSU breeding lines from the Gulf-Atlantic Wheat Nursery, USDA Uniform Southern Soft Red Winter Wheat Nursery, and Southern University Prelim were screened during the 2010 and 2011 cycles in Kenya for resistance to Pgt in cooperative nurseries sponsored by the USDA-ARS and International Maize and Wheat Improvement Center (Centro Internacional de Mejoramiento de Maíz y Trigo, Spanish acronym CIMMYT). This included about 60 advanced breeding lines from the LSUAC program each year along with several hundred lines that are part of the five-university Sungrains partnership. The SUNPRE-Early and SUNPRE-Late nurseries were also screened in 2011. These nurseries are part of the six-university regional small grain breeding collaborative and include about 160 elite breeding lines. A stem rust screening nursery was set up at the Ben Hur Research Farm in Baton Rouge that permitted effective field screening of over 1200 varieties and breeding lines from university and USDA-ARS programs across the Southeastern US.
There were 309 new crosses added to the LSUAC wheat breeding program in 2011 and 96 of these included stem rust resistance as a specific objective of the cross. Many of the crosses were topcross/three-way or backcrosses made to pyramid effective Sr genes and permit MAS enrichment of populations for specific Sr gene combinations. Sr genes in crosses include: Sr2, Sr24, Sr26 (Agnus), Sr36, SrAmigo, Sr22, Srtmp, Sr35, Sr42 (Norin 40) and several unique and uncharacterized genes. MAS will be used in the fall to enrich populations of three-way (topcross) F1s by elimination of those F1 plants that do not contain target Sr genes. Additional germplasm was obtained from other Sungrains breeders and USDA-ARS collaborators, including the ARS Eastern Wheat genotyping Lab and CIMMYT stem rust nurseries.