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Research Project: Genetic Improvement of Small Grains for Biotic and Abiotic Stress Tolerance and Characterization of Pathogen Populations

Location: Plant Science Research

Title: Molecular characterization of a new powdery mildew resistance gene Pm54 in soft red winter wheat

Author
item HAO, YUANFENG - International Maize & Wheat Improvement Center (CIMMYT)
item Parks, Wesley
item Cowger, Christina
item CHEN, ZHENBANG - University Of Georgia
item WANG, YINGYING - University Of Georgia
item BLAND, DAN - University Of Georgia
item MURPHY, J - North Carolina State University
item GUEDIRA, MOHAMMED - North Carolina State University
item Brown-Guedira, Gina
item JOHNSON, JERRY - University Of Georgia

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2014
Publication Date: 12/23/2014
Citation: Hao, Y., Parks, W.R., Cowger, C., Chen, Z., Wang, Y., Bland, D., Murphy, J.P., Guedira, M., Brown Guedira, G.L., Johnson, J. 2015. Molecular characterization of a new powdery mildew resistance gene Pm54 in soft red winter wheat. Theoretical and Applied Genetics. 128:465-476.

Interpretive Summary: Powdery mildew has caused increasing damage to wheat production in the southeastern USA. To combat the disease, there is a continuing need to discover new genes for mildew resistance and incorporate them in commercial wheat varieties. Pioneer® variety 26R61 (shortened as 26R61) and the variety AGS 2000 have been used as check varieties in a regional nursery for a decade, and have provided good mildew resistance across regions. This study focused on the mildew resistance in a population descended from a cross of 26R61 and AGS 2000. The mildew resistance of 178 progeny from this cross was assessed in the field in Plains, GA and Raleigh, NC in both 2012 and 2013. Three genes providing a significant level of partial resistance were consistently detected on wheat chromosomes 2BL, 4A and 6BL, respectively. The gene on chromosome 2BL was contributed by 26R61 and was different from Pm6, a widely used gene in the Southeast region. The other two genes came from AGS 2000, and probably are new sources of wheat mildew resistance. The resistance on chromosome 6BL was found to behave like a single gene in growth chamber tests. Since there is no known gene for mildew resistance on this particular chromosome of common wheat, the gene was given a new designation, PmA2K. A closely linked molecular marker, Xbarc134, should be useful when putting PmA2K and other mildew resistance genes into the same wheat line.

Technical Abstract: Powdery mildew has caused increasing damage to wheat production in the southeastern USA. To combat the disease, there is a continuing need to discover new genes or quantitative trait loci for mildew resistance and promptly adopt those loci in breeding programs. Pioneer® variety 26R61 (shortened as 26R61) and AGS 2000 have been used as checks in the Uniform Southern Soft Red Winter Wheat Nursery for a decade, and have provided good mildew resistance across regions. In the present study, genetic analysis of mildew resistance was conducted in a RIL population from a cross of 26R61 and AGS 2000. Phenotypic evaluation was conducted in the field in Plains, GA and Raleigh, NC in 2012 and 2013, for a total of four environments. Three QTL of major effect were consistently detected on wheat chromosomes 2BL, 4A and 6BL, respectively. The 2BL QTL contributed by 26R61 was different from Pm6, a widely used gene in the Southeast region. The other two QTL from AGS 2000 probably represent new loci for mildew resistance. The 6BL locus was subsequently characterized as a simple Mendelian factor when the population was inoculated with a single Blumeria graminis f. sp. tritici (Bgt) isolate in controlled environments. Since there is no known Pm gene on this particular location of common wheat, the gene was designated PmA2K. The closely linked marker Xbarc134 was highly polymorphic in a set of mildew differentials, indicating the marker should be useful in pyramiding PmA2K with other Pm genes by marker-assisted selection.