Theses and Dissertations at Montana State University (MSU)
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Item Population dynamics of wheat stem sawfly, Cephus cinctus Norton, in barley in Montana(Montana State University - Bozeman, College of Agriculture, 2020) Achhami, Buddhi Bahadur; Chairperson, Graduate Committee: David K. Weaver; Gadi V. P. Reddy, Jamie D. Sherman, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Antixenosis, antibiosis, and potential yield compensatory responses in barley cultivars exposed to wheat stem sawfly under field conditions' which is contained within this dissertation.; Gadi V. P. Reddy, Jamie D. Sherman, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Effect of precipitation and temperature on larval survival of Cephus cinctus (Hymenoptera: Cephidae) in barley cultivars' which is contained within this dissertation.; Robert K. D. Peterson, Jamie D. Sherman, Gadi V. P. Reddy and David K. Weaver were co-authors of the article, 'Multiple decrement life tables of Cephus cinctus Norton (Hymenoptera: Cephidae) across a set of barley cultivars: the importance of plant defense versus cannibalism' which is contained within this dissertation.; Gadi V. P. Reddy, Megan L. Hofland, Robert K. D. Peterson, Jamie D. Sherman and David K. Weaver were co-authors of the article, 'Host selection and oviposition behaviors of Cephus cinctus (Hymenoptera: Cephidae) in barley' which is contained within this dissertation.Wheat stem sawfly (WSS) is an economically devastating pest of cereals grown in North America. The larva is the only feeding stage and remains confined within a host stem until it emerges as an adult the following year. This limited mobility increases larval vulnerability to mortality factors when host plant traits are hostile to survival. For instance, larval mortality is greater in barley than in solid stemmed wheat cultivars known to be resistant. Both solid stemmed wheat and barley kill neonates via host plant resistance traits. Traditionally, barley was recommended as an alternative rotational crop to prevent WSS outbreaks in wheat crops. There is limited data available regarding barley host plant resistance and questions persist. Has barley resistance changed over time? What is the impact of larval feeding injury on grain yield of barley? Do females display similar oviposition behaviors across barley cultivars that vary in susceptibility? To answer these questions. I conducted field experiments to assess resistance and possible tolerance to WSS in eight barley cultivars. Based on the number of eggs, 'Hockett' was the most attractive cultivar to WSS female (less antixenosis), while 'Craft' and 'Celebration' killed the greatest number of neonates due to antibiosis. Multiple decrement life table studies revealed that plant defense and cannibalism were two major causes of larval mortality. We measured greater yield in infested stems with dead larvae (potential tolerance) than for cut stems and both were greater than uninfested stems in all cultivars except 'Celebration'. A greenhouse study revealed that females preferred 'Hockett' over 'Craft' in frequencies of oviposition behaviors and numbers of eggs deposited. Additionally, a greater amount of the WSS attractant (Z)-3-hexenyl acetate was found in aerations from 'Hockett' plants than from 'Craft.' The amount of defensive compound linalool was greater in aerations from 'Craft' than from 'Hockett.' These results suggest that barley cultivars are equipped with varying levels of antibiosis, antixenosis, and tolerance traits against WSS. Thus, we can exploit these traits in the development of cultivars which can reduce WSS populations and decrease economic loss caused by this species.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.