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 Transformation of Gaeumannomyces graminis and the fate of transforming DNA(Montana State University - Bozeman, College of Agriculture, 1991) Pilgeram, Alice LaRayne; Co-chairs, Graduate Committee: Don E. Mathre and Joan HensonItem Effects of carboxin, an oxathiin systemic fungicide, on cell permeability and DNA dependent RNA synthesis(Montana State University - Bozeman, College of Agriculture, 1971) Shively, Owen DanielItem 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 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 Integrated management of Cercospora leaf spot on sugar beet(Montana State University - Bozeman, College of Agriculture, 2004) Larson, Ben James; Chairperson, Graduate Committee: Barry J. Jacobsen.Cercospora leaf spot (CLS), caused by Cercospora beticola, is the most important foliar disease of sugar beets in Montana. Losses in research plots ranging from 5-15 metric tons per hectare and 0.5-1.5% lower sugar in the last 7 years. Increased levels of storage rot, sugar impurities, and loss of sugar to molasses have also contributed to losses. Current management strategies are heavily dependent upon the application of a few registered fungicides. Continued use of these fungicides is threatened by registration removal through the Food Quality Protection Act of 1996, and the development of fungicide resistance in Cercospora beticola. This study examined management strategies for CLS integrating host-plant resistance, a CLS prediction model, registered fungicides, and a Bacillus mycoides biocontrol agent, BmJ. The effects of these strategies on disease development and yield were evaluated in field trials from 2001 to 2003. Disease levels were rated 4-5 times per season to generate a disease value for each treatment quantified as the area under the disease progress curve. Yield was determined as metric tons of beets and kilograms of extractable sucrose per hectare, and percent sucrose. Results showed more resistant varieties to give equal disease control with 1-2 fewer fungicide applications than more susceptible varieties without sacrificing yield in moderate to light CLS pressure. BmJ applications (4/year) reduced disease levels below the accepted economic threshold and gave disease control equal to fungicide applications when mixed with a single spray of a half rate of tetraconazole at disease onset. BmJ was highly effective in CLS management when combined with more resistant varieties. The levels of C. beticola fungicide resistance to benomyl, azoxystrobin and tetraconazole isolated from research plots in 2001 and 2002 were measured by spore germination and mycelial growth assays. Total insensitivity to benomyl was observed in more than 70% of isolates and reduced sensitivity to azoxystrobin and tetraconazole up to 10 ppm was also recorded. Preliminary results indicate growing more resistant varieties of sugar beet and spraying BmJ may aide in managing fungicide resistance by reducing the number of fungicide applications necessary for CLS control.Item Mycofumigation with Muscodor albus : effects on Verticillium wilt and black dot root rot of potato, effects on Glomus intraradices and ectomycorrhizal fungi, and M. albus proliferation in soil(Montana State University - Bozeman, College of Agriculture, 2008) Grimme, Eva; Chairperson, Graduate Committee: Barry J. Jacobsen.Muscodor albus Worapong, Strobel & Hess, isolate CZ-620 (MA) is an endophytic fungus that produces volatile organic compounds (VOCs) and non-volatile antimicrobial compounds. The use of these VOCs to inhibit or kill a wide range of microorganisms is termed mycofumigation. This dissertation focuses on parameters of MA mycofumigation including: production and bioactivity of previously un-described water-soluble antimicrobial compounds produced by MA; distribution of antimicrobial compounds from a MA point source in three soil types as measured by effects on Verticillium dahliae and Colletotrichum coccodes; control of V. dahliae and C. coccodes on potato; the ability of MA to colonize soil; and the effects of mycofumigation on ectomycorrhizal fungi (EMF) in vitro and on the colonization of onion roots by the arbuscular mycorrhizal (AM) fungus Glomus intraradices. The bioactivity of water-soluble compounds produced in potato dextrose broth was significantly increased as measured in growth reduction of C. coccodes, V. dahliae, and Rhizoctonia solani. No reduction was observed for Aphanomyces cochlioides and Pythium ultimum. Antimicrobial compounds from a MA colonized barley point source reduced V. dahliae and C. coccodes populations in soils by 60-100% at distances up to 9 cm from the inoculation source depending on soil type. Mortality rate ranging from 70-100% was observed within a 3 cm radius from the inoculation source. In both field and greenhouse trials, MA colonized barley formulation reduced Verticillium wilt and black dot root rot severity and reduced populations of both pathogens in potato tissue as measured by real-time quantitative PCR and serial dilution. Planting directly into mycofumigated soil previously infested with V. dahliae or C. coccodes resulted in equal control of the pathogens when compared to a one-week mycofumigation period prior to planting. After six weeks of incubation MA did not colonize sterile soil further than 0.5 cm away from a MA inoculation point. In vitro experiments showed that most of the tested EMF were inhibited in the presence of MA VOCs, but were able to resume growth when removed from VOCs. Incorporating MA into soil had no negative but supportive effect on onion root colonization by the AM fungus G. intraradices.Item Cultivar susceptibility and fungicide control of black dot root rot(Montana State University - Bozeman, College of Agriculture, 2007) Meyer, Jack Robert; Chairperson, Graduate Committee: Barry J. Jacobsen.Black Dot (Colletotrichum coccodes) is an important potato disease worldwide causing reported yield losses in the 10-30% range. It is involved in the early dying disease complex along with Verticillium dahliae or V. albo atrum, and root lesion nematodes. Besides early dying, black dot also causes silvery blemishes on the tuber surface that resemble those of silver scurf which results in reduced value in fresh markets. The purpose of this work was to evaluate North American cultivars for black dot tolerance and to evaluate fungicides for their efficacy in controlling this disease. To evaluate cultivar resistance, thirty-four commercial cultivars were evaluated in inoculated, greenhouse experiments for susceptibility to C. coccodes. Plant growth was then evaluated 60 days post inoculation. Inoculated plants were stunted and had reduced dry weight of 0% to 53.6% when compared to un-inoculated controls. Significant reductions in growth were observed for 25 of the 34 cultivars (P<0.05).