Theses and Dissertations at Montana State University (MSU)
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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 Pest management challenges and climate change in water limited winter wheat agroecosystems in southwestern Montana(Montana State University - Bozeman, College of Agriculture, 2020) Nixon, Madison Grace; Chairperson, Graduate Committee: Fabian D. MenalledDryland winter wheat production is influenced by many environmental factors including climate, disease, and resource availability. In Montana, Bromus tectorum (cheatgrass) and Fusarium pseudograminearum (a fungus causing root crown rot) are major winter wheat pests; reducing yield and grain quality. However, little is known how climate change and resource availability impact winter wheat, B. tectorum, and F. pseudograminearum individually as well as their multi-trophic interactions. Thus, this research aimed to 1) Determine the susceptibility of B. tectorum to F. pseudograminearum and assess how CO 2 and nitrogen impact their growth, and 2) Evaluate how elevated temperature, reduced precipitation, and plant competition impact winter wheat and B. tectorum growth and reproduction. Utilizing growth chambers, high and low nitrogen treatments, fungal inoculated and uninoculated treatments, and ambient and elevated CO 2 treatments, Bromus tectorum was found to be a host of F. pseudograminearum, and the fungus significantly reduced root, shoot and total biomass, as well as primary physiological processes of B. tectorum. Fusarium pseudograminearum infection was not impacted by nitrogen or CO 2 level. Low nitrogen increased emergence and root production early on, while high nitrogen increased shoot production at later growth stages. Low nitrogen also improved stomatal conductance and transpiration rate. High CO 2 increased B. tectorum root, shoot, and biomass production, as well as intercellular CO 2. An interaction between ambient CO 2 and low nitrogen resulted in the greatest shoot relative growth rate between the first and second harvest. Field tests, using three climate treatments (ambient, increased temperature, reduced precipitation with increased temperature) and three plant competition levels (monoculture winter wheat, monoculture B. tectorum, and biculture of the two), found that for both winter wheat and B. tectorum monocultures, ambient and warmer climates produced similar yields and biomass, respectively, whereas the drier with warmer treatment reduced these factors. Additionally, B. tectorum presence increased winter wheat grain protein. A quadratic interaction model of winter wheat yield as a function of B. tectorum biomass by climate treatment suggests that at low to moderate B. tectorum biomass levels, winter wheat yield was negatively impacted by the warmer and drier treatment, whereas ambient and warmer treatment results were similar.Item Management of Kochia (Bassia scoparia) in a time of herbicide resistance(Montana State University - Bozeman, College of Agriculture, 2020) Lim, Charlemagne Ajoc; Chairperson, Graduate Committee: Alan T. Dyer; Alan Dyer and Prashant Jha were co-authors of the article, 'Kochia (Bassia scoparia) growth and fecundity under different crops and weed densities' submitted to the journal 'Weed science journal' which is contained within this dissertation.; Alan Dyer and Prashant Jha were co-authors of the article, 'Survival and reproductive fitness of glyphosate-resistant kochia (Bassia scoparia) in the presence of glyphosate' submitted to the journal 'Weed technology journal' which is contained within this dissertation.; Alan Dyer and Prashant Jha were co-authors of the article, 'Survival, growth and fecundity of Dicamba-resistant kochia (Bassia scoparia) in the absence and presence of Dicamba' submitted to the journal 'Weed technology journal' which is contained within this dissertation.Kochia [Bassia scoparia (L.) A. J. Scott] is one of the most troublesome weeds in the US Great Plains. This is exacerbated by the development of herbicide-resistant kochia populations which necessitates more ecologically driven approaches for its control. This research examined the competitive effects of four crops (sugar beet, soybean, barley and corn) in combination with kochia densities (3, 13, 24, 47, 94 and 188 plants m-2) on kochia development and kochia seed production. Corn had greatest effect in reducing kochia biomass and seed production. Barley had greatest effect in delaying kochia flowering which happened after barley senesced at 113 days after kochia emergence. Soybean and sugar beet had the least effect in reducing kochia biomass and seed production, respectively, relative to fallow. This research also reports the fitness of glyphosate-resistant kochia and dicamba-resistant kochia in the presence and absence of glyphosate and dicamba selection, respectively, under field conditions. Glyphosate-resistant kochia showed limited fitness cost (less seed weight and seed radicle length relative to the susceptible) in the absence of glyphosate selection and reduced reproductive fitness (seed production) in the presence of increasing glyphosate selection. In the absence of dicamba selection, dicamba-resistant kochia showed a fitness cost (reduced growth and seed production relative to the susceptible) associated with dicamba resistance with greater fitness cost observed with increased level of resistance. Dicamba-resistant kochia also showed reduced reproductive fitness (seed production) in the presence of increasing dicamba selection. Overall, this research provides information on the growth and reproductive fitness of glyphosate-resistant kochia and dicamba-resistant kochia in the presence and absence of glyphosate and dicamba selection, respectively. Furthermore, this research provides insights on the competitive abilities of different but financially viable rotational crops for kochia management in Montana.Item Gap colonization in grasslands of the Northern Great Plains(Montana State University - Bozeman, College of Letters & Science, 1996) Payson, Elizabeth MaryItem Spotted knapweed (Centaurea maculosa Lam) : water, nutrients, plant competition, bacteria, and the seed head fly (Urophora affinis Frnfd.)(Montana State University - Bozeman, College of Agriculture, 1996) Kearing, Stephen AnthonyItem Belowground competition and response to defoliation of Centaurea maculosa and two native grasses(Montana State University - Bozeman, College of Agriculture, 2005) Sartor, Karla Anne; Chairperson, Graduate Committee: Catherine A. Zabinski.Invasion of native rangelands in the western United States has serious ecological and economic effects. Understanding the mechanisms behind invasion of Centaurea maculosa (spotted knapweed) is necessary to effectively manage this species. Arbuscular mycorrhizae (AM), which are a type of plant fungal symbiosis, are ubiquitous in grasslands. My research explores the role of AM for increasing the competitive ability of C. maculosa. A greenhouse experiment tested the effects of AM fungi and neighbor species on growth of C. maculosa, Festuca idahoensis (Idaho fescue) and Pseudoroegneria spicata (bluebunch wheatgrass). A mesh barrier permeable to AM hyphae allowed comparison of species interactions by either roots and/or AM hyphae in pots without a barrier or by AM hyphae alone in pots with a barrier. Centaurea maculosa plants had high AM colonization levels within roots and ERH (extraradical hyphae), and may have increased AM colonization of neighboring plants. I found no evidence, however, that ERH affected competition, as C. maculosa neighbors had the greatest effect on native grass neighbors there was the potential for root contact. Additionally, plants grown with AM fungi were always smaller than non-mycorrhizal plants. In the second experiment, I investigated growth response after herbivory (simulated by clipping), with different neighboring species and AM fungi. Centaurea maculosa, F. idahoensis and P. spicata were grown in the greenhouse with a C. maculosa neighbor, with or without AM fungi, and with one of three clipping treatments (no clipping, focal plant clipped or neighbor plant clipped to remove 75% of aboveground biomass). Compensatory growth was dependent on AM fungi and neighbor species. Centaurea maculosa compensated for herbivory only when grown with a conspecific and with AM fungi, or with a F. idahoensis neighbor and no AM fungi. Clipping decreased AM colonization in F. idahoensis only, and colonization also decreased in F. idahoensis when C. maculosa neighbors were clipped. This research suggests that AM fungal effects vary between species in the grassland system, and is important for determining plant species response to herbivory. I also find that high levels of herbivory may reduce C. maculosa biomass enough to be a method for weed control, but neighbor species is important to determining plant response to herbivory.