Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Consider the roots: examining barley belowground in the search for adaptation(Montana State University - Bozeman, College of Agriculture, 2024) Williams, Jessica Lynn; Chairperson, Graduate Committee: Jamie Sherman; This is a manuscript style paper that includes co-authored chapters.Barley is important for global food security and sustaining the economically valuable malt industry. Montana is a top barley producer in the United States, but terminal drought stress poses a significant threat to this production by negatively impacting yield and quality. New crop varieties with enhanced environmental adaptation and soil resource extraction would help address this and other issues facing modern agriculture. Stay-green is a trait that extends grain fill in cereals and can stabilize yield and quality under drought. However, this trait and its benefits can be inconsistent across environments and its successful incorporation into breeding strategies would benefit from expanded understanding of stay-green. Roots may play a role in stay-green physiology. Roots provide plants with the water and nutrients needed for growth and are important for crop performance in their own right. Different root system architectures provide adaptation to different environmental stressors, but studying these belowground structures is challenging. Adaptation is also impacted by soil properties and microbial communities. For this dissertation, roots were examined in greenhouse seedling assays and field trials in Montana. Agronomic performance was also assessed for malt barley and spring wheat cultivars varying for stay-green, a biparental barley population segregating for stay-green, and a diverse mapping population of barley lines from different breeding programs. Stay-green cultivars had a greater percentage of deep roots, more prolonged root growth during grain fill, and greater yield. Analysis of the biparental population identified genetic co-segregations of stay-green, root phenotypes, grain quality, and quality stability between environments, further supporting the benefit of stay-green in dry environments and its connection to roots. The diverse mapping population was used to find associations between the relative abundances of bacteria in the rhizosphere and barley genetic loci, that were mostly environment specific. Rhizospheric bacteria may be involved in local adaptation of plants. Finding plant genetic signal for these microbial characteristics supports the idea that it may be possible to breed crops with enhanced ability to recruit beneficial microbiomes if environmental influence and agronomic impact can be understood. Root examination remains a challenging but worthwhile avenue to pursue in crop adaptation research.Item Genetic analysis of productive tiller number and green leaf duration under late-seasoned heat and drought stress environment in spring wheat(Montana State University - Bozeman, College of Agriculture, 2010) Naruoka, Yukiko; Chairperson, Graduate Committee: Luther E. Talbert.Climate change is affecting the growing environment for spring wheat (Triticum aestivum L. em. Thell) in the northern Great Plains, challenging breeders to identify traits and genes that will allow reliable grain yield under drought and heat stress conditions. The first objective of this study was to evaluate the genetic basis of productive tiller number (PTN) and its relationship to economic traits under a wide range of environments. Correlation of PTN with economic traits was determined using three recombinant inbred line populations. Quantitative trait loci (QTL) analysis was conducted with a mapping population generated from a cross between Reeder and Conan. Our results showed a consistent positive correlation between PTN and grain yield under drought and heat stress conditions as well as well-watered conditions across three spring wheat populations. The major stable QTL, QTn.mst-6B, was consistent across environments and populations, and the positive allele from Reeder increased grain yield. The second objective of this study was to evaluate the genetic basis of green leaf duration (GLDAH) which has been reported as a drought and heat stress resistant trait in several crops. Additionally, the relationship of GLDAH to agronomic traits and a root trait was assessed using the Reeder/Conan population. Correlation analysis showed a positive relationship between GLDAH and test weight, seed weight, seed diameter under heat and drought stress conditions but not cool, well-watered conditions. In contrast, GLDAH had a neutral relationship with grain yield under the stress conditions, but showed negative correlation under well-watered conditions. Major QTL QGfd.mst-4A had a consistent effect under hot, dry conditions for the populations. The Reeder allele of QGfd.mst-4A resulted in longer GLDAH and also increased the amount of xylem exudate, indicating higher root mass and/or activity. These results suggested that i) QTn.mst-6B may be useful for improvement of spring wheat production under a wide range of environment and ii) QGfd.mst-4A may contribute to heat and drought stress resistance potentially through root function, but may negatively affect grain yield under well-watered conditions in the northern Great Plains of North America and similar environments.