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United States Department of Agriculture

Agricultural Research Service

Research Project: CEREAL RUST FUNGI: GENETICS, POPULATION BIOLOGY, AND HOST-PATHOGEN INTERACTIONS

Location: Cereal Disease Laboratory

Title: Complementary epistasis involving Sr12 explains adult plant resistance to stem rust in Thatcher wheat (Triticum aestivum L.)

Authors
item Rouse, Matthew
item Talbert, Luther -
item Singh, Davinder -
item Sherman, Jamie -

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2014
Publication Date: April 24, 2014
Citation: Rouse, M.N., Talbert, L.E., Singh, D., Sherman, J.D. 2014. Complementary epistasis involving Sr12 explains adult plant resistance to stem rust in Thatcher wheat (Triticum aestivum L.). Theoretical and Applied Genetics. Available: http://link.springer.com/article/10.1007/s00122-014-2319-6.

Interpretive Summary: Wheat adult plant resistance (APR) to stem rust is desirable for it can be race non-specific. Resistance derived from cultivar Thatcher can confer high levels of APR to Ug99 stem rust when combined with stem rust resistance gene Sr57 (Lr34). Researchers have characterized the inheritance of APR in cultivar Thatcher as complex. In order to identify the loci providing APR in Thatcher, we evaluated 160 lines derived from Thatcher crossed to susceptible cultivar McNeal for field stem rust reaction in Kenya for two seasons, in St. Paul for one season, and at the seedling stage with races TTKSK (Ug99) and SCCSC. Segregation of seedling resistance to race SCCSC was consistent with the presence of a single major gene: Sr12. All lines and parents were susceptible as seedlings to race TTKSK. However, adult plant stem rust severities in Kenya varied from 5% to 80%. Genetic mapping identified regions associated with stem rust resistance in at least one season. Three QTL were inherited from Thatcher and one, Sr57, was inherited from McNeal. The markers closest to the QTL peaks were used to determine the interaction among the genes. Resistance on choromosome arm 3BS was detected in all three environments and explained 27-35% of the phenotypic variation. The peak of this region was at the same location as Sr12. Interactions were significant between Sr12 and chromosome arms 1AL and 2BS. Though Sr12 was statistically associated with resistance, lines with Sr12 were not always resistant. The data suggest that Sr12 or a linked gene, though not effective to Ug99 alone, confers APR when combined with other resistance genes.

Technical Abstract: Adult plant resistance (APR) in wheat (Triticum aestivum L.) to stem rust, caused by Puccinia graminis f. sp. tritici, is desirable because this resistance can be race non-specific. Resistance derived from cultivar Thatcher can confer high levels of APR to the virulent P. graminis f. sp. tritici race TTKSK (Ug99) when combined with stem rust resistance gene Sr57 (Lr34). Researchers have characterized the inheritance of APR in cultivar Thatcher as complex. In order to identify the loci providing APR in Thatcher, we evaluated 160 RILs derived from Thatcher crossed to susceptible cultivar McNeal for field stem rust reaction in Kenya for two seasons, in St. Paul for one season, and at the seedling stage with races TTKSK and SCCSC. Segregation of seedling resistance to race SCCSC was consistent with the presence of a single major gene: Sr12. All RILs and parents were susceptible as seedlings to race TTKSK. However, adult plant stem rust severities in Kenya varied from 5% to 80%. Composite interval mapping identified four quantitative trait loci (QTL) with an LOD greater than 3.0 in at least one season. Three QTL were inherited from Thatcher and one, Sr57, was inherited from McNeal. The markers closest to the QTL peaks were used in an ANOVA to determine the additive and epistatic effects. A QTL on 3BS was detected in all three environments and explained 27-35% of the variation. The peak of this QTL was at the same location as Sr12. Epistatic interactions were significant between Sr12 and QTL on chromosome arms 1AL and 2BS. Though Sr12 cosegregated with the largest effect QTL, lines with Sr12 were not always resistant. The data suggest that Sr12 or a linked gene, though not effective to race TTKSK alone, confers APR when combined with other resistance loci.

Last Modified: 10/25/2014
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