Germplasm Development and Molecular Studies for Important Traits to Improve Texas Wheat Production
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Wheat production in Texas is limited by several abiotic and biotic stresses. Abiotic stresses are drought and heat. Biotic stresses include both diseases and insects. In the high plains, Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and greenbug, in addition to drought, are major problems (USDA-NASS, 2010). In the south of Texas, wheat rusts, powdery mildew, and heat are major factors that limit yield. At times, Hessian fly can be severe problems throughout the state. Because of these biotic and abiotic stresses, variety improvement and yield enhancement in Texas is extremely challenging. Because pathogens evolve with host resistance genes, single major resistance genes, may only be effective for a few years. Therefore, slow rusting resistance genes and quantitative trait loci (QTL) for adult plant resistance to several diseases have been identified and incorporated together with single genes (Singh et al. 1993). Biotypes of insects keep changing too. Greenbug biotypes changed from A to E, I, and K (Weng et al. 2010) and RWA changed from 1 to 2 (Haley et al. 2004). New Hessian fly biotypes have defeated resistant sources in eastern soft red winter wheat regions (Cambron et al. 2010). This situation pushes researchers to keep searching for new sources of resistance and new genes in currently available sources of wheat or its relatives. Compared to disease and insect resistances, drought and heat tolerance are more complicated. The measurements of physiological traits under drought and heat conditions are not always reliable due to unstable environments and the limited accuracy of equipment. Scientists have worked hard to identify traits or parameters that are highly correlated with drought and heat tolerance and use them as a measurement of tolerance to abiotic stress. In recent years, progress in wheat genetic and genomic research has been accelerated due to improved techniques and readily available information. In addition to abundant expressed sequence tag (EST) sequence, DNA array technology (DArT) markers, and simple sequence repeat (SSR) markers, high throughput single nucleotide polymorphic (SNP) markers have been designed and are currently being used (Chao et al. 2010). As most available SSR markers are not very diagnostic for specific genes, SNP markers offer promising results, with increased efficiency and accuracy. With improved understanding of the wheat genome and new molecular techniques, the process of developing superior germplasm lines and adapted cultivars can be sped up. This project will deploy both precision phenotyping and molecular techniques to characterize mechanisms of abiotic and biotic stresses. Molecular lab, growth chamber, greenhouse, field experiments will be conducted to identify and validate diagnostic markers linked to target genes/QTL controlling important traits. Germplasm lines containing multiple favorable traits including high yield and good end-use quality will be developed.