Scholarship & Research
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Item Tritrophic responses to signaling formulations sprayed in wheat stem sawfly-infested field plots(Montana State University - Bozeman, College of Agriculture, 2019) Caron, Christopher G.; Chairperson, Graduate Committee: Scott PowellThe wheat stem sawfly (Cephus cinctus Norton) is an economically important pest of wheat in the Northern Great Plains of North America. Producers and researchers are continuing to search for an effective management strategy. A combination of management tactics, such as host-plant resistance and biocontrol, may be the best method to suppress wheat stem sawfly (WSS) populations. My study examines whether direct toxicity, induced host-plant resistance, or the manipulation of tritrophic interactions, can be achieved through the application of signaling molecules in WSS-infested plots. The overall objective was to assess whether signaling molecules could be incorporated as a management tactic for WSS. Field experiments assessed whether aqueous applications of methyl jasmonate (MeJA), methyl salicylate (MeSA), and Actigard? influence WSS fitness, host-plant fitness, or the recruitment of natural enemies. Treatments were applied in WSS-infested plots for 3 consecutive weeks in both 2017 and in a second experiment in 2018. Wheat samples were collected before harvest and processed to assess parameters of infestation and parasitism. Plant growth and yield parameters were also recorded. The field trials suggested that MeJA and Actigard? induced significant changes that can impact tritrophic interactions in winter wheat. No effect was observed from the applications of MeSA. WSS fitness parameters decreased with applications of MeJA. MeJA treated plots had decreased infestation (2017), decreased larval weight (2018), and increased neonate mortality (2018). Actigard? treated plots had decreased larval weight and increased recruitment of clerid beetles (Phyllobaenus dubius Wolcott) (2017). Treatments of MeJA decreased stem height and grain weight, while treatments of Actigard? decreased grain weight in 2017. Although many of these findings were not consistent for both growing seasons, this study demonstrates the potential for these signaling molecules to manipulate the interactions between the WSS, or its host plant, and associated natural enemies in winter wheat.Item Rhizobiome dynamics in plant growth promotion and abiotic stress response(Montana State University - Bozeman, College of Agriculture, 2023) Goemann, Hannah Marie; Chairperson, Graduate Committee: Brent M. PeytonSoil microorganisms play vital roles in global nutrient cycling. Understanding the complex relationships between plants and soil microbes and their implications is one of the greatest challenges facing microbial ecology today. Soil microbes can play beneficial roles in supporting plant growth by increasing access to nutrients, water, and decreasing plant stress signaling under abiotic stresses such as drought and heat. With increasing climate variability due to climate change, it is imperative to make scientifically informed management decisions to best support global biodiversity and plant productivity in natural and agroecosystsms. In this dissertation I summarize four separate investigations of plant-microbe interactions. The first is using nitrogen-fixing cyanobacterial biofertilizers to promote plant growth of perennial second generation bioenergy crops switchgrass (Panicum virgatum) and tall wheatgrass (Agropyrun elongatum). The second and third studies seek to better understand plant-microbe carbon exchange under drought stress in the native North American prairie grass blue grama (Bouteloua gracilis). The final study explores the potential microbial contribution to heat tolerance of panic grass (Dichanthelium lanuginosum) across a natural soil temperature gradient in Yellowstone National Park. Next-generation amplicon sequencing using the Illumina Miseq platform is the primary technique utilized across the three studies to investigate microbial community dynamics. The main results of the biofertilizer study were that tall wheatgrass is better suited to the SW Montana growing season than switchgrass, and similar plant yields were achieved with the cyanobacterial biofertilizer as with urea chemical fertilizer without negatively impacting the microbial community diversity. The first blue grama study found that severe and mild drought had distinct, phylogenetically linked responses within the blue grama rhizobiome with Planctomycetes, Thermoproteota (ammonia-oxidizing archaea), and Glomeromycetes (arbuscular mycorrhizal fungi) exhibiting notably altered relative abundances. The second blue grama study found that climate legacy plays an important role in shaping blue grama drought response. Finally, from the D. lanuginosum study in Yellowstone National Park we learned that pH and temperature both strongly influence community composition, and that D. lanuginosum selects for unique community members in its rhizosphere at higher temperatures. Collectively, these studies contribute to furthering our understanding of the dynamics of plant-associated microbiomes.Item Factors affecting coleoptile lengths at leaf emergence, days to emergence, and relative growth rate in covered and hullness, two- and six-rowed barley (Hordeum vulgare L. and Hordeum distichum L.)(Montana State University - Bozeman, College of Agriculture, 1965) Schneiter, Albert A.Item The effect of osmotic stress on growth characteristics of two spring wheat varieties(Montana State University - Bozeman, College of Agriculture, 1961) Richardson, GlennItem Effects of low frequency electromagnetic fields on biological systems : experimental results and theoretical models(Montana State University - Bozeman, College of Engineering, 1991) Mohr, Timothy AllenItem Effects of N and P fertilizers on the growth, nodulation and N 2-fixation of fababean (Vicia faba L.), green pea (Pisum sativum L.) and dry bean (Phaseoulus vulgaris L.)(Montana State University - Bozeman, College of Agriculture, 1985) Koala, SaidouItem Post-logging stand characteristics and crown development of whitebark pine (Pinus albicaulis)(Montana State University - Bozeman, College of Letters & Science, 1992) Kipfer, Todd RogerItem The effect of previous cutting on apparent carbohydrate storage and spring growth of perennial grasses with a comparison of methods of determining apparent carbohydrate storage(Montana State University - Bozeman, College of Agriculture, 1949) Cooper, Clee S.Item Characterization of the Arabidopsis compact inflorescence (cif) mutant and isolation of CIF1 to ACA10, a P-type IIB CA²�-ATPase gene(Montana State University - Bozeman, College of Letters & Science, 2003) George, Lynn DeAnnItem Evaluation of tall willows (Salix spp.) within a livestock grazing allotment in southwest Montana(Montana State University - Bozeman, College of Agriculture, 1994) Manoukian, Mark Edward