Theses and Dissertations at Montana State University (MSU)
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Item Characterization and assessing fungicide sensitivity of Fusarium spp. causing root rot and wilt in lentils in the northern Great Plains(Montana State University - Bozeman, College of Agriculture, 2022) Bugingo, Collins; Chairperson, Graduate Committee: Mary Burrows; This is a manuscript style paper that includes co-authored chapters.Fusarium root rot and wilt are yield limiting diseases caused by Fusarium spp. in lentils globally. Seedborne Fusarium species and races of Fusarium oxysporum f. sp. lentis (Fol) have not been characterized. The sensitivity of commonly used fungicides on prevalent species is not fully known. In 2019 and 2020 commercial lentil fields were surveyed and seed lots collected from infected patches and further isolation, morphological and molecular characterization was conducted in the laboratory. Additional isolates and lentil seed were received from Washington, Montana, Idaho, North Dakota, southern Canada, and Spain for fungicide, seedborne Fusarium spp. and race-characterization of Fol respectively. In addition to assessing presence of seedborne Fusarium pathogens on the seed coat, the cotyledon and embryo were assessed for the presence of Fusarium spp. Fungicide sensitivity was assessed using mycelial assays and an additional spore assay for pyraclostrobin. A total of 84 seed lots from the Northern Great Plains (NGP) were assayed where a total of 486 and 228 Fusarium isolates were isolated in 2019 and 2020, respectively and all the representative isolates were virulent with a 1.5-4.5 root rot severity rating. Most isolates were found in the seed coat (57- 75%), cotyledon (19-23%) and embryo (6-20%) for the 2019 and 2020 isolates, respectively. F. oxysporum and F. acuminatum were all either sensitive or intermediately sensitive to prothioconazole and ipconazole. A total of 51 isolates were race-typed and 9 races identified whereby race 7 and 1 were the predominant at 53% and 16%, respectively. This study underscores the importance of understanding Fusarium spp. composition in lentil production, role of seedborne inoculum, fungicide efficacy in root rot/wilt management and race composition upon developing effective Integrated Pest Management (IPM) strategies.Item Aphanomyces euteiches spatial distribution, host studies, and characterization in Montana(Montana State University - Bozeman, College of Agriculture, 2022) Murphy, Carmen Yvette; Chairperson, Graduate Committee: Mary BurrowsGrowing pulse crops in Montana has been inhibited by biotic constraints to production, including a complex of pathogens causing root rot. Aphanomyces root rot, caused by the soilborne oomycete, Aphanomyces euteiches, causes plant stunting and yellowing, root browning and constriction, and reduces yield in dry pea and lentil in the state. Twelve fields with a history of pulse root rot were sampled in northeast Montana with three 100 m entrance transects and one 50 m transect at a low spot or problem area. Soil from each 10 m quadrat within transects was assessed for root rot using a greenhouse bioassay with a susceptible dry pea variety, and with PCR. Samples were also analyzed for soil properties and nutrients. Distribution of the pathogen was sporadic in most fields, except for fields that had been growing pulses in a consistent rotation, where root rot severity was high and consistent. Soil pH, organic matter, potassium, and sulfur concentration were correlated with Aphanomyces root rot, and isolates varied in their response to acidic pH in vitro. Using a highly virulent A. euteiches isolate, greenhouse trials were conducted to assess the pathogen load of inoculated soil after growing host and non-host plant species, measured with a bioassay. Greenhouse pots were inoculated with 500 oospores per gram prior to planting plant treatments. Growing host plants resulted in higher root rot severity on dry pea bait plants compared to non-host plant treatments. When five cycles of plants were grown in greenhouse pots inoculated with A. euteiches, using five 'rotation' treatments, one treatment with three consecutive rounds of non-host plants reduced the disease severity score in one trial repetition compared to treatments with less than three successive rounds growing a non-host. This research indicates that sampling strategies for Aphanomyces root rot requires multiple sampling locations within a field to enhance the probability of detection, and that crop rotation is an important tool for management of pathogen load in the soil.Item Role of crop fertility and seed treatments in managing fusarium root rot of lentil (Lens culinaris Medikus) in the northern Great Plains(Montana State University - Bozeman, College of Agriculture, 2021) Atencio, Sydney Christine; Chairperson, Graduate Committee: Perry Miller and Mary Burrows (co-chair)Lentil is a relatively new but economically important crop for the state of Montana, along with surrounding states in the northern Great Plains. Comparatively little is known about the basic fertility of lentil, and importance of inoculant type on lentil. Additionally, the rise of pulse crop acres in the northern Great Plains, has given rise to root rot pathogens, such as Fusarium root rot. Fusarium root rot of pulses, has a wide host range, limiting the efficacy of rotation in its management. This research is comprised of two main studies. Field trials occurred at sites in Bozeman, Havre, Moccasin, and Sidney in 2019 and 2020. The objective of chapter two was to evaluate the effect of rhizobial inoculant formulations (granular vs. seed-coat/peat-powder) and nutrient additions (potassium, sulfur, and a micronutrient fertilizer), on lentil establishment, growth, seed protein, and yield. For chapter two, in six of eight site-years there was no yield difference between inoculant types. Applications of sulfur (S) fertilizer increased yield at three of eight site-years by an average of 303 kg ha-1 (17%) compared to treatments without S. Results from this study further suggest the importance of S fertilization for lentil. The objective for chapter three was to evaluate seed treatments' ability to control Fusarium root rot on lentil establishment, growth, disease severity and yield. In three of eight site-years, the inoculated control had a relatively high disease severity compared to other seed treatments. In general, treatment responses varied across site-year due to low disease pressure. Additionally, F. graminearum and F. oxysporum were isolated at a high frequency from control plots at sites in 2019. Data from 2020 is pending.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 Population dynamics of coexistence by plant pathogens of the rhizosphere of spring wheat(Montana State University - Bozeman, College of Agriculture, 2015) Troth, Erin Elizabeth Gunnink; Chairperson, Graduate Committee: Alan T. DyerThe dryland root rot complex is a collection of root pathogens that significantly affect small grain production in the semiarid regions world-wide. The complex includes Cochliobolus sativus, Fusarium pseudograminearum, Rhizoctonia solani, Pythium ultimum, and Penicillium sp. The purpose of this thesis was to document the interactions among these pathogens that commonly coexist within the wheat rhizosphere. The thesis had two objectives: 1) examine variation in interactions amongst isolates of C. sativus and F. pseudograminearum within the wheat crown and 2) identify interactions among pathogens in the dryland root rot complex (C. sativus, F. pseudograminearum, R. solani, P. ultimum, and Penicillium sp.) in-field, as reflected in plant response variables. For objective 1, wheat in both field and greenhouse settings were inoculated singly and in all pathogen isolate combinations. Both C. sativus and F. pseudograminearum, alone and in combination, reduced yield (P<0.001, P=0.003, respectively), but C. sativus isolates had a greater effect on both yield and emergence (P<0.001). Inoculations with some isolates of C. sativus and F. pseudograminearum were suppressive on populations of each other. Significant variability in suppressiveness was observed among isolates for both species. For objective 2) plant health as measured by emergence, vigor, plant height and yield, was observed in response to inoculations with all single, pairwise, four-pathogen and five-pathogen combinations of C. sativus, F. pseudograminearum, R. solani, P. ultimum, and Penicillium sp. Antagonistic relationships that favored overall plant health were observed between several pathogens, including P. ultimum, Penicillium sp. and C. sativus. These antagonistic interactions affected seedling emergence and plant vigor. Conversely, F. pseudograminearum in combination with R. solani significantly reduced emergence beyond expected (P=0.002). Within the community interaction studies overall, F. pseudograminearum was the dominant pathogen, causing more disease and more consistent disease than any other pathogen, and generating increased damage to emergence when inoculated in the community (P=0.017). In conclusion, interactions among members of the dryland root rot complex is a dynamic process, one that varies by species and pathogen isolate. These interactions are more often antagonistic, with one pathogen suppressing another. Additional studies may improve how disease control measures are deployed in the future.Item The potential for the occurrence of Rhizoctonia root rot in cereal crop production areas of Montana(Montana State University - Bozeman, College of Agriculture, 1992) Hudak, Joseph Michael; Co-chairs, Graduate Committee: Jack Riesselman and Don E. MathreItem Biological control of Rhizoctonia root rot of pansy, petunia and basil(Montana State University - Bozeman, College of Agriculture, 1998) Hickey, Kathleen AnneItem Effects of systemic fungicides and potassium fertilizers on disease intensity, yield components, and grain yield of common root rot diseased barley(Montana State University - Bozeman, College of Agriculture, 1984) Shefelbine, Paul ArthurItem The role of bacteria in the root and crown rot complex of irrigated sainfoin (Onobrychis viciifolia Scop.) in Montana(Montana State University - Bozeman, College of Agriculture, 1978) Gaudet, Denis AndrewItem Effect of sterol-biosythesis inhibiting fungicides on take-all of spring wheat caused by Gaeumannomyces graminis var. tritici(Montana State University - Bozeman, College of Agriculture, 1986) Garcia, Celsa