Rigor, Alex T.2009-02-192009-02-192008-12https://hdl.handle.net/11299/47668University of Minnesota dissertation. December 2008. Major: Applied plant sciences. Advisor: James A. Anderson. 1 computer file (PDF); v, 71 pages, appendices I-III.Preharvest sprouting (PHS) is the precocious germination of the grains in the spike following physiological maturity. In wheat, the main problem associated with PHS is reduction in end-product quality. White wheats are the most susceptible class of wheat to PHS whereas the red wheats have high levels of resistance due to the pleiotropic effect of the red color genes with dormancy. However, recent studies reported that several sources of resistance to PHS are available in white wheat germplasm. Our objective was to map quantitative trait loci (QTL) associated with PHS resistance in a recombinant inbred population of 94 lines from a cross between Grandin*5/ND614-A, an elite hard white spring wheat susceptible to PHS and NY6432-18/Clark's Cream 40-1, a soft white winter wheat selected for its high level of PHS resistance. Multiple interval mapping analysis revealed seven QTL for PHS based on the combined data across eight environments over three years (2005-2007). The QTL on chromosomes 2D, 5A and 7A had LOD score ≥ 2.5 and were not associated with QTL for plant height and heading date. These three QTL jointly explained 39.4% of the phenotypic variation for PHS. Other QTL were found on chromosomes 1B, 4B, 6A and 6D that explained 2.1% to 14.2% of the phenotypic variation. A significant QTL x QTL interaction was found between the chromosomal regions in 1B and 2D that explained 5.5% of the phenotypic variation. The 4B and 6A QTL coincided with chromosomal regions associated with plant height. The 4B QTL explained only 5.2% phenotypic variation for PHS, but 58% of phenotypic variation for plant height. Conversely, the QTL on chromosome 6A explained the largest phenotypic variation for PHS (14.2%) of any individual QTL, but accounted for only 5% of the phenotypic variation for plant height. Overall, the results indicated the complexity of the genetic architecture of PHS and a strong genotype x environment interaction and trait correlations. Some of the QTL found in this study may aid in marker-assisted breeding for improvement of PHS resistance in wheat.en-USCorrelationMultiple Interval MappingPHSPreharvest SproutingQTL MappingWhite WheatApplied plant sciencesThesis or Dissertation