Mapping Genes for Resistance to Multiple Diseases in Soft Red Winter Wheat.

Mapping Genes for Resistance to Multiple Diseases in Soft Red Winter Wheat

Carpenter, Neal¹, Carl Griffey¹, Subas Malla¹, Marla Hall², Amir Ibrahim³, J. Paul Murphy⁴, David Marshall⁵, Myron Fountain⁵, Eugene Milus⁶, Jerry Johnson⁷, Shiaoman Chao⁸, and Gina Brown-Guedira⁹.

¹Dept. of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, VA 24061; ²Limagrain Cereal Seeds, 6414 N. Sheridan, Wichita, KS 67204;  ³Soil and Crop Sciences Department, Texas A&M University, 2474 TAMU, College Station, TX 77843; ⁴Dept. of Crop Science, North Carolina State University, Raleigh, NC 27695; ⁵USDA-ARS Plant Science Research Unit, Raleigh, NC 27695; ⁶Dept. of Plant Pathology, University of Arkansas, Fayetteville, AR 72701; ⁷Dept. of Crop and Soil Science, University of Georgia, Griffin, GA 30223; ⁸USDA-ARS Cereal Crops Research Unit, Fargo, ND 58102; and ⁹USDA-ARS Eastern Regional Genotyping Center, Raleigh, NC  27695.

Leaf rust caused by Puccinia triticina and stripe rust caused by Puccinia striiformis are destructive pathogens of wheat (Triticum aestivum).  Host resistance is the most economical solution for providing full season control and reducing damage due to these diseases as opposed to use of multiple fungicide applications.  Pyramiding of multiple genes into single cultivars and use of quantitative trait loci (QTL) conferring adult plant resistance (APR) is the best strategy to achieve durable resistance.  It is difficult to pyramid multiple genes through traditional phenotypic selection because of the lack of biotype/pathotype specific populations to discern the presence of individual resistance genes among genotypes.  The soft red winter wheat cultivar Jamestown is productive in the southern Corn Belt, the Deep South, and throughout the mid-Atlantic region including Virginia.  This can be attributed to its combined resistance to leaf rust, stripe rust, and Hessian fly (Mayetiola destructor).  Phenotypic data was collected at diverse locations for resistance to leaf rust (NC, TX and VA) and stripe rust (AR, NC, TX, and VA) in two primary mapping populations, Pioneer25R47 / Jamestown (P47/JT) and FG95195 / Jamestown (FG/JT) comprised of 170 and 186 F8:9 recombinant inbred lines (RIL), respectively.  Both public and proprietary single nucleotide polymorphism (SNP) markers were used by Monsanto Company to initially genotype 42 of the P47/JT RILs having contrasting phenotypes. Subsequently, a set of 142 RILs were genotyped with public 90K SNP. Bulk segregant analysis was used to select microsatellite markers (SSRs) associated with resistance to leaf rust and stripe rust.  Linkage maps were constructed using JoinMap. Windows Cartographer (WinQTLCart version 2.5) was used to identify putative QTL.  Initial analysis of the P47/JT population identified two consistent QTL located on chromosomes 1B and 6A that are associated with leaf rust infection type and severity.  The variation explained by putative leaf rust resistance QTL of Jamestown on 1B and 6A was 3.3 % to 6.6% (Additive = -0.27 to -0.37) and 4.3% to 8.9% (Additive = -2.1 to -2.9).  The QTL on 1B was flanked by wsnp_Ku_c4271_7774388 and Kukri_c31554_437 (4.86 cM interval).  The most diagnostic marker for the QTL on 6A was RAC875_c104548_369; flanked by Tdurum_contig81516_69 and Barc146 (4.6 cM interval).  Initial results also identified two consistent QTL associated with stripe rust infection type and severity in the P47/JT population that are located on chromosomes 3B and 6A.  The variation explained by putative stripe rust resistance QTL of Jamestown on 3B and 6A was 5.4 % to 6.9% (Additive = -0.23 to -0.26) and 0.1% to 8.1% (Additive = -0.06 to -0.49).  The QTL on 3B was flanked by GWM285 and wsnp_JD_c17082_16025440 (5.2 cM interval). The most diagnostic marker for the QTL on 6A was Barc146; flanked by RAC875_c104548_369 and D_GBUVHFX01CSU22_382 (13.5 cM interval). These QTL are being validated in the FG/JT population and a second year of phenotypic data will be collected and analyzed in 2015.