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Oral: Host Plant Resistance


Mapping of two QTL conferring adult plant resistance to Puccinia graminis f. sp. tritici race TTKSK (Ug99) and evidence for race specificity
J. BRIGGS (1), M. Rouse (2), S. Bhavani (3), C. Hiebert (4) (1) University of Minnesota, U.S.A.; (2) USDA-ARS, U.S.A.; (3) CIMMYT, Kenya; (4) Agriculture and Agri-Food Canada, Canada

The durability of wheat stem rust (caused by Puccinia graminis f. sp. tritici) resistance is strengthened by the use of multiple broad-spectrum sources of resistance. Adult plant resistance (APR) is thought to provide partial effect, race non-specific resistance. APR was observed in the Ecuadorian bread wheat cv. Morocho Blanco (MB) in field tests at Njoro, Kenya. MB is susceptible to TTKSK (Ug99) at the seedling stage. A doubled haploid (DH) population was created from a cross between MB and the susceptible line LMPG-6 to identify loci associated with APR phenotypes. Eighty-eight DH lines were genotyped with approximately 90,000 SNPs using a custom Infinium assay from Illumina. Sixty-seven additional DH lines (MB x LMPG-6) and seventy-three recombinant inbred lines (MB x Faller) were used to verify SNPs associated with reduced levels of stem rust infection. Severity and infection type were assessed on adult plants in Njoro, Kenya from 2013-2015, Debre Zeit, Ethiopia in 2015, and in single race nurseries inoculated with races RCRSC, TPMKC, QTHJC, and QFCSC in Rosemount, USA from 2014-2015. Two QTL that reduce stem rust severity were identified on chromosome arms 2BS and 6AS in the three screening seasons in Kenya. However, in Ethiopia only 6AS was effective, and in the USA only 2BS was effective to race QFCSC. The current data indicates that a singular race and location should not be used to develop lines using APR as possible genotype x race interactions exist.