Wheat quality, marketability, and profitability are threatened by the risks of sprouting damage. Development of wheat varieties with improved sprouting resistance will mitigate the risk of sprouting and increase the production of high quality wheat; however, breeding efforts for improved sprouting resistance are limited by time- and labor-intensive phenotyping and by the lack of major-effect loci associated with sprouting resistance which are independent of grain color. The wheat growing regions of the Pacific Northwest and the Great Lakes are particularly vulnerable to sprouting related quality issues because the high-value soft white winter wheat varieties grown in those areas are susceptible to sprouting damage induced by frequently rainy conditions between physiological and harvest maturity. Sprouting damage is the result of precocious germination prior to grain harvest (preharvest sprouting, PHS) and the enzymatic degradation of the starchy endosperm by elevated alpha-amylase activity (αAmy). Sprouting damage is affected by genetic factors such as gibberellin sensitivity, grain color and maturity, by environmental factors such as temperature and moisture, and by the interaction of genotype and environment. The objectives of this dissertation were to: 1) develop standardized phenotyping protocol which produce consistent, reliable results across environments and can be practically implemented to improve phenotypic selection in breeding programs; 2) associate sprout resistance phenotypes with specific loci that might be leveraged to improve sprouting resistance; and 3) utilize sprouting resistance alleles from the wild-wheat relative Aegilops tauschii to reduce sprouting damage in wheat. Preharvest sprouting rating criteria and a modified enzyme assay were developed to phenotype elite wheat varieties, breeding lines, and experimental wheat populations in replicated field trials. Genome wide association analysis (GWAS) was used to identify significant quantitative trait loci (QTL), and genome-wide regression models were used to predict genomic estimated breeding values (GEBVs) for sprouting resistance. Standardized phenotyping methods were validated for the characterization of PHS and αAmy and were used for phenotyping in all succeeding studies. Additionally, significant sprout resistance loci were identified by GWAS, and genetic values for improved PHS resistance were successfully predicted by GS. Finally, advantageous genetic loci derived from Ae. tauschii were identified which are significantly associated with improved PHS resistance. To improve genetic gain for sprouting resistance in wheat, the methods described herein will enable more accurate selection of superior genotypes through improved phenotyping methods, genomic selection, and pyramiding of significant QTL using marker assisted selection.
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