Theses and Dissertations at Montana State University (MSU)
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Item The impact of Teosinte branched1 and reduced height mutations in durum wheat(Montana State University - Bozeman, College of Agriculture, 2021) Brown, McKenna Margaret; Chairperson, Graduate Committee: Michael J. GirouxIncreasing the yield of wheat requires identifying new genetic combinations of alleles by crossing or by creating variation in yield limiting genes. Wheat yield is impacted by tiller number and seeds per tiller, both of which are impacted by the Reduced height (Rht) and Teosinte branched1 (TB1) genes. In this study, durum plants varying for Rht and TB1 alleles created by EMS mutagenesis were studied to determine the impact of each allele upon agronomic and seed traits. Both projects aimed to increase durum yield, one through an increase in tiller number; the other through the development of a plant with height between current full-height and semi-dwarf varieties that can allocate more resources to seed production. The impact of TB1 null alleles were studied alone and together in greenhouse and field trials, along with an RNA sequencing study to determine the impact of TB1 mutation upon global gene expression in developing meristems. TB1 single and double null mutants produced more biomass and tillers per plant, and expression of genes in meristems varied. A screen of wheat varieties grown in Montana identified that several spring and durum wheat varieties contain different TB1 alleles, but none contained TB1 null alleles. Rht experiments included field trials, coleoptile length and gibberellic acid responsiveness assays, and an in-vitro test to determine the impact of each Rht mutation upon binding to Gibberellin Interacting Domain 1 (GID1) that directly influences plant height. It was found that the previously described Rht-B1b-E529K allele reduced both plant height and coleoptile length while two newly characterized Rht mutations had lesser impacts with trends towards intermediate-height plants. The results of this research demonstrate that Rht alleles that alter RHT binding to GID1 and TB1 null alleles may prove useful in increasing durum tillering and optimizing plant height for different growing conditions.Item Genetic dissection of grain yield and yield component traits in hexaploid spring wheat(Montana State University - Bozeman, College of Agriculture, 2020) Jones, Brittney Hannah; Chairperson, Graduate Committee: Michael J. Giroux; Nancy K. Blake, Hwa-Young Heo, Jay R. Kalous, John M. Martin, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Improving hexaploid spring wheat by introgression of alleles for yield component traits from durum wheat' in the journal 'Crop science' which is contained within this dissertation.; Nancy K. Blake, Hwa-Young Heo, Jay R. Kalous, John M. Martin, Deanna L. Nash, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Impact of yield component alleles from durum wheat on end-use quality of spring wheat' in the journal 'Cereal chemistry ' which is contained within this dissertation.; Nancy K. Blake, Hwa-Young Heo, John M. Martin, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Allelic response of yield component traits to resource availability in spring wheat' in the journal 'Theoretical and applied genetics' which is contained within this dissertation.Hexaploid wheat accounts for 30% of global grain production, ranking in the top three major food crop species along with maize and rice. Grain yield from hexaploid wheat is an important agronomic consideration for sustainable agriculture. As the human population continues to grow and the amount of farmable land decreases it is imperative that a focus be placed on improving grain yield performance. Grain yield is a quantitative trait and as such improved performance is largely influenced by genetic variation, environment and genotype x environment interactions. Due to the quantitative nature of grain yield the mechanisms of genetic control are largely unknown. The purpose of the presented research was to genetically dissect grain yield and yield component traits in hexaploid spring wheat grown in Montana in order to leverage new understanding to improve Montana germplasm and future breeding programs. This investigation included three research aims: (i) to determine the genetic impact of introgressed durum yield component alleles on hexaploid spring wheat agronomic and end-use quality performance (Chapters 2 and 3); (ii) investigate how resource availability as simulated by plant competition and seed density impacted yield component allele response at four yield component quantitative trait loci (Chapter 4); and (iii) to better understand the mechanism of genetic control of QTn.mst-6B a quantitative trait locus associated with tiller number through high-resolution mapping (Chapter 5). This research highlights the complexity of pleotropic interaction among yield component traits and variability associated with grain yield as impacted by environment and resources availability. Results from the three aims provide a detailed investigation of single quantitative trait loci for use as novel sources of cultivar improvement and increased genetic gain as well as, a better understanding of grain yield and yield component traits.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.