Theses and Dissertations at Montana State University (MSU)
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Item Iron nutrition of plants and interactions with vascular wilt disease and light(Montana State University - Bozeman, College of Agriculture, 1989) Macur, Richard EugeneThe relationship between iron nutritional status and Verticillium Wilt disease in tomato possessing single gene resistance to Race 1 of Verticillium dahliae was investigated using hydroponic culture media. Iron limiting conditions increased the sensitivity of resistant tomatoes to the pathogen as expressed by wilting and chlorosis. Distance of fungal vascular invasion was approximately the same in both iron replete and iron limited treatments. Comparison of near-isolines revealed that the magnitude of disease expressed in Fe deficient Pixie II (resistant) was considerably less than that expressed by the susceptible Pixie variety. Infection of tomato did not enhance iron stress severity as quantified by root peroxidase activity and chlorophyll content of young leaves. The release of iron from horse spleen ferritin through photochemical reduction of Fe(III) to Fe(II) was studied in vitro. Spectrophotometric measurement of the Fe(ferrozine)3^2+ complex (specific for Fe(II)) was used to quantify rates of Fe mobilization: Cool white fluorescent plus incandescent light effectively promoted the rate of Fe release. Compounds known to be present in plants may provide further regulation of photorelease. Reductive removal from ferritin was inhibited by phosphate, and hydroxide, whereas citrate, oxalate, tartrate, and caffeate enhanced the release. Of the organic acids studied, caffeate was the only compound which induced detectable Fe release in the absence of irradiation. Rate constants ranged from 2.7 x 10^-3 sec^-1 (pH = 4.6) to 2.1 x 10^-3 sec^-1 (pH = 7.1) at 26.5°C. Synthesis of the photosynthetic apparatus is dependent on both light and iron. Thus, the findings provide one possible mechanism coupling chloroplast iron demand with iron release from ferritin. Treatments known to alter either phenolic metabolism or overall enzyme activity were utilized to examine the Fe reductive mechanisms involved in iron stress response at the roots. Although specific compounds caused elevation of internal o-dihydroxyphenol content, the overall root reduction capacity of Fe stressed plants was significantly suppressed. However, plant roots retained significant capacity to reduce Fe after tissues were subjected to severe protein denaturizing treatments. Thus, indications for both secreted reductant and enzymatic reduction mechanisms were observed.Item Cephalosporium stripe of winter wheat: disease processes and effects(Montana State University - Bozeman, College of Agriculture, 1967) Pool, Robert Alfred FrankItem Etiology of Cephalosporium stripe in relation to the expression of resistance in cultivars of winter wheat (Triticum aestivum L.)(Montana State University - Bozeman, College of Agriculture, 1979) Morton, Joseph BrianItem The effect of Cephalosporium gramineum on yield components of various winter wheat genotypes(Montana State University - Bozeman, College of Agriculture, 1972) Johnston, Robert HowardItem 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 Optimal crop sequences to control cephalosporium stripe in winter wheat(Montana State University - Bozeman, College of Agriculture, 1987) Danielson, Joan Gay; Chairperson, Graduate Committee: M. Steve Stauber; Oscar Burt (co-chair)Cephalosporium gramineum, a soil borne fungus, causes a stripe disease in winter wheat. The fungus restricts the flow of water and nutrients to the plant head resulting in significant yield losses. The disease is passed from winter wheat crop to winter wheat crop through Cephalosporium stripe infested straw. Rotating to non-host spring crops or fallow, allowing time for decomposition of infested residue, is the primary means of controlling Cephalosporium stripe. The objective of this thesis was to determine economically optimal land use sequences to control Cephalosporium stripe in winter wheat. Control of the disease is a stochastic dynamic problem and as such was formulated within a stochastic dynamic programming framework. The economic criterion used was maximization of expected present value of returns over variable cost. The model was applied to a representative dryland grain farm in the Judith Basin of central Montana. The decision alternatives were winter wheat, barley, and fallow. The state variables included in the model were previous land use, years of control, level of Cephalosporium stripe infection in the last winter wheat crop, barley price, and winter wheat price. Transformation functions were derived for all of the state variables. Based on statistically estimated transformation functions, transition probability functions were developed for the stochastic state variables: past Cephalosporium stripe infection level, winter wheat price, and barley price. The relationship between Cephalosporium stripe infection level and winter wheat yield was also estimated. The optimal policy is dominated by fallow and barley decisions when there are less than four years of control unless the past infection level is very low. Once three years of control has been exceeded, winter wheat decisions become optimal at higher levels of past infection and increase as winter wheat prices increase. Finally, it is evident that consideration of at least a three-year control sequence would increase annual returns significantly regardless of the past Cephalosporium stripe infection level.Item Bacterial wilt management : a prerequisite for a potato seed certification program in Mali(Montana State University - Bozeman, College of Agriculture, 2007) Thera, Aissata Traore; Chairperson, Graduate Committee: Barry J. Jacobsen; Florence Dunkel (co-chair)Potato is one of the most important cash crops in Mali and has been well adapted to the Malian cropping systems and food habit. Bacterial wilt caused by Ralstonia solanacearum (Smith) Yabuuchi et al., (1995) has become a major problem causing important damage in production. The Race and biovar of the bacterium present in Mali were not known at the start of this thesis research and the objective of this research was to identify the race/biovar and to evaluate integrated control methods with the aim to produce high quality disease free seed potato in Mali. We have initially identified the biovar and Race of R. solanacearum affecting potato in Mali as Race 1 biovar 3. ELISA tests were used on soil and water samples to detect the presence of R. solanacearum. Three detections methods of the bacteria (bacterial streaming test, Agdia immunostrip test and Tetrazolium chloride media) in plant samples were compared; weeds and crops hosting the bacteria as sources of inoculums were identified using Agdia immunostrip test.