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Title: QTL mapping of adult plant resistance to Ug99 stem rust in the spring wheat population RB07/MN06113-8

Author
item BAJGAIN, PRABIN - UNIVERSITY OF MINNESOTA
item ROUSE, MATTHEW
item BHAVANI, SRIDHAR - INTERNATIONAL MAIZE & WHEAT IMPROVEMENT CENTER (CIMMYT)
item ANDERSONJ, JAMES - UNIVERSITY OF MINNESOTA

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2015
Publication Date: 8/4/2015
Citation: Bajgain, P., Rouse, M.N., Bhavani, S., Andersonj, J. 2015. Mapping QTL conferring adult plant resistance to Ug99 in the University of Minnesota biparental population RB07/MN06113-8. Molecular Breeding. 35:170.

Interpretive Summary: Wheat stem rust is a fungal disease of wheat that decreases yield. A strain of the wheat stem rust fungus known as Ug99 emerged in Uganda in 1999 and threatens global wheat production because it is able to infect nearly all wheat varieties. Two United States spring wheat breeding lines possess partial resistance to Ug99 at the adult plant stage in Kenya and Ethiopia. We assessed a biparental popoulation derived from these two lines for resistance in the field to Ug99 in Africa. We found one consistent quantitative resistance locus across all environments on chromosome arm 2BS. Finding of this potentially new locus conferring adult plant resistance to Ug99 in United States spring wheat suggests that wheat breeders in the United States can obtain resistance to Ug99 by selecting within convential germplasm. The molecular markers that we identified as linked to stem rust resistance can also be validated for use in wheat breeding to select for resistance to Ug99. The identification of the resistance locus on 2BS and linked molecular markers will facilitate the improvement of resistance of United States wheat cultivars to the dangerous Ug99. Ug99 resistant wheat cultivars will protect United States wheat production from yield loss if a Ug99 epidemic were to occur in the United States.

Technical Abstract: The emergence and spread of the Ug99 race group of the stem rust pathogen in the past decade has exposed the vulnerability of wheat to this disease. Discovery of novel and effective sources of resistance is vital to reduce losses. The experimental breeding line MN06113-8 and cultivar RB07 developed by the University of Minnesota wheat breeding program exhibited adult plant resistance (APR) to the Ug99 race group in field tests in Kenya and Ethiopia. Both of these lines are susceptible at the seedling stage to isolates of the Ug99 race group. To dissect the genetic mechanism of resistance present in these lines, MN06113-8 was crossed to RB07 to generate 141 F6 recombinant inbred lines (RILs). The RIL population was evaluated for APR to Ug99 in Kenya and Ethiopia over three seasons; and for stem rust resistance to North American stem rust pathogen races in St. Paul, MN in one season. Composite interval mapping detected six quantitative trait loci (QTL) involved in APR to African stem rust pathogen races and three QTL involved in stem rust resistance to North American stem rust pathogen races. One QTL located on chromosome 2B was observed in all environments and could be a new source of APR to stem rust pathogen races. Development of diagnostic markers linked to this gene will facilitate marker assisted selection of resistant lines to generate varieties with elevated levels of APR to the Ug99 race group.