Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Impact of the D genome and quantitative trait loci on quantitative traits in a spring bread wheat by spring durum wheat cross(Montana State University - Bozeman, College of Agriculture, 2014) Kalous, Jay Robert; Chairperson, Graduate Committee: Luther E. TalbertDesirable agronomic traits are similar for common hexaploid (6X) bread wheat (Triticum aestivum, 2n = 6x = 42, genome, AABBDD) and tetraploid (4X) durum wheat (T. turgidum durum, 2n = 4x = 28, genome, AABB). However, bread and durum wheat are genetically isolated from each other due to an unequal number of genomes that cause sterility when crossed. Previous work allowed identification of a 6X and 4X parent that when crossed resulted in a large number of recombinant progeny at both ploidy levels. In this study, interspecific recombinant inbred line populations at both 4X and 6X ploidy with 88 and 117 individuals, respectively, were developed from a cross between Choteau spring wheat (6X) and Mountrail durum wheat (4X). Lines within each population contained a mixture of alleles from each parent for loci in the A and B genomes. The presence of the D genome in the 6X population resulted in increased yield, tiller number, and seed size. The D genome also resulted in a decrease in stem solidness, lower test weight and fewer seed per spike. Similar results were found with a second RIL population containing 152 lines from 18 additional 6X by 4X crosses. Several additional QTL for agronomic and quality traits were identified in both the 4X and 6X populations. Positive durum alleles increasing kernel weight in hexaploids, on chromosomes 3B and 7A may be useful for introgression by bread wheat breeders.Item Candidate gene association mapping in spring wheat(Montana State University - Bozeman, College of Agriculture, 2011) Kalous, Jay Robert; Chairperson, Graduate Committee: Luther E. Talbert.Association mapping (AM) is a form of quantitative trait locus (QTL) mapping that utilizes a collection of germplasm rather than a structured mapping population. Marker/trait associations are made through the application of a mixed-effects model that corrects for population stratification. The objective of this study was to evaluate the application of association mapping on a selection of elite spring wheat cultivars. We tested marker/trait associations for known "perfect" markers and markers identified as controlling traits of interest through traditional bi-parental mapping. We also wanted to evaluate the observed linkage disequilibrium (LD) surrounding genes of interest by utilizing closely linked sets of markers in specific regions of the spring wheat genome. Population structure was estimated with fifty-one unlinked microsatellite markers. Two phenotypic datasets were used for evaluation. The first was an unbalanced historical dataset, and the second was a balanced dataset taken from a two year replicated field trial. Marker/trait associations were identified for plant height, stem solidness, heading date, grain protein content, test weight, and seed color. Our analyses identified significant associations between Rht-D1 and plant height, Ppd-D1 and heading date, and Xgwm340 and stem solidness. No associations were identified between Rht-B1 and plant height, Ppd-B1 and heading date, nor Vrn-B1 and heading date. The extent of LD varied depending on breeding history and selection pressure. One LD block was identified around the stem solidness QTL and two blocks were found surrounding a productive tiller QTL. Smaller blocks of LD were observed surrounding the three genes controlling kernel color. No LD was observed surrounding the Rht-B1 locus.