Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
14 results
Search Results
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 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, CelsaItem Root rot of sweet peas(Montana State University - Bozeman, College of Agriculture, 1957) Olsen, Carl M.Item Proof of pathogenicity of Fusarium slani (Mart.) Appel & Wr. to sainfoin (Onobrychis viciifolia Scop.) and development of procedures to select for resistance(Montana State University - Bozeman, College of Agriculture, 1976) Auld, Dick Lindsey