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 Effects of a barley chromosome 6H grain protein QTL on agronomic traits, malt quality traits, and stomatal control under two irrigation and nitrogen fertilization regimes(Montana State University - Bozeman, College of Agriculture, 2018) Mangel, Dylan J. L.; Chairperson, Graduate Committee: Andreas FischerCereal grain protein concentration (GPC) is an important quality parameter, with high GPC desirable when grain is used for food or feed, while low (typically below 12- 13%) GPC is needed when barley grain is used for malting. A major QTL controlling grain protein has previously been identified on barley chromosome 6H. Based on the comparison with a co-linear region on wheat chromosome 6B, the functional status of a gene coding for a NAC transcription factor (HvNAM-1) is responsible for controlling whole-plant senescence, nutrient remobilization from leaves to developing grains, and grain protein concentration. In this context, the purpose of this study was the analysis of the influence of a low- vs. a high-grain protein allele at this locus on barley agronomic and malting quality parameters in different genetic backgrounds. Integration of the low-protein allele stably lowered GPC by 1.6-1.8%, in both years and across all combinations of genetic backgrounds and management practices. Lines with the low-protein allele matured 1.4 to 2.5 days later, dependent on management, and had stably lower malt protein and diastatic power. Effects on additional agronomic and malt quality parameters including yield, test weight, percentage of plump kernels, free amino nitrogen and alpha-amylase activity were subtler and depended on the genetic background tested. Our data also provide important information on the influence of soil N and water availability on malt quality characteristics. Overall, use of the chromosome 6H low-grain protein allele stably lowered grain and malt protein levels without important negative influences on any of the tested agronomic and malt quality parameters, indicating its usefulness in the development of new malting barley germplasm. The studied chromosome 6H GPC QTL also controls expression of a gene coding for a glycine-rich RNA-binding protein (HvGR-RBP1) that may improve drought tolerance. Stomatal conductance and canopy thermal imaging assays did not show consistent effects of the allelic state of the GPC QTL on stomatal control. However, our data showed important correlations between stomatal conductance, canopy temperature depression and agronomic parameters including yield, demonstrating the value of the performed assays for variety selection and breeding.