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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 Creating rust resistance in wheat via modification of host genes(Montana State University - Bozeman, College of Agriculture, 2020) Nyamesorto, Bernard Mensah; Chairperson, Graduate Committee: Li Huang; Hongtao Zhang and Li Huang were co-authors of the article, 'Wheat MYC4 transcriptional factor gene modification enhanced host resistance against rust pathogens' which is contained within this dissertation.; Dissertation contains an article of which Bernard Mensah Nyamesorto is not the main author.A major challenge to resistance breeding in bread wheat (Triticum aestivum L.) is limited genetic diversity. The traditional approach to combating this problem is introgression of resistant genes from other closely related species into elite but susceptible cultivars. This strategy is often associated with linkage drag. Moreover, pathogens continue to evolve into different and more virulent forms (races) that overcome these resistant genes in a process called resistance breakdown. A typical example is the outbreak of Ug99, a novel African stem rust pathotype that exhibited virulence against numerous stem rust resistance genes. Creating resistance within wheat's own genome is a panacea to the challenges surrounding the traditional method. Biotrophic plant pathogens such as wheat rusts are known to manipulate host genes as a means of overcoming host defense response and acquiring nutrients. Central to wheat-rust interactions is highly sophisticated immune repertoire consisting of diverse signal perception and intracellular signaling pathways which are regulated by transcriptional regulators and co-factors. Unfortunately, pathogen effector proteins also take advantage of host plant genes (so called pathogen susceptible host genes) including transcriptional mechanisms. Hence editing the genes targeted by these pathogens in wheat is a valuable means of creating host resistance that has been neglected. We conducted these studies to identify host genes targeted by rust pathogens through bioinformatics approaches including transcriptome analysis which showed that wheat NPR1 genes (transcriptional regulator) and MYC4 and MY21 (transcription factors) are negatively involved compatible wheat-rust interactions. Subsequently, when these genes were down regulated in susceptible Chinese Spring using Barley Mosaic Virus Induced Gene Silencing (BSMV) assay, the silenced plants became resistant to rust pathogens. Loss-of-function mutations created in these homeologs via Ethyl methanesulfonate mutagenesis conferred resistant to rust pathogens. Consequently, this study led to the development of new rust resistance germplasms.Item An assessment of nematodes affecting wheat in Montana(Montana State University - Bozeman, College of Agriculture, 2018) Al-Khafaji, Riyadh Talib; Chairperson, Graduate Committee: Alan T. DyerNematodes represent a major biological constraint on wheat and barley production worldwide, and yet no comprehensive assessment of plant parasitic nematodes associated with cereals has been conducted for Montana. To address this shortcoming, a survey was conducted to determine the species of plant parasitic nematodes associated with small grains, and an assessment of variation in virulence across 4 crops and 8 resistant wheat lines was conducted for Pratylenchus neglectus populations collected from across Montana. The survey, conducted across 11 counties, and found widespread distribution of P. neglectus, Tylenchorhynchus spp., and Tylenchus spp. within the state. Populations of P. neglectus were generally low (268 to 363 nematodes/kg of dry soil for 2015 and 2016, respectively). However, destructive populations were detected in 9 fields in both 2015 and 2016. In addition, populations of the cereal cyst nematode Heterodera avenae were detected. Cereal cyst nematode Heterodera filipjevi, a regulated pest, was detected in only one field. Additional species of parasitic nematode were detected, but rare. To assess the applicability of resistant crops and wheat lines for management of P. neglectus, greenhouse trials were conducted using nematode populations from within the state. In two trials conducted with resistant crops, significant interaction was detected between crops and populations of nematodes (ANOVA P< 0.001 and P= 0.01). In the first trial, populations from 3 counties were virulent on barley (mean reproductive factor = 10.9). Populations from other counties were either non-virulent on barley, or their inoculations were ineffective. In the second trial, 2 of the 3 populations were again virulent on barley (mean Rf = 4.4 and Rf = 10.7). Trials examining virulence across resistant wheat lines found no interactions between populations and wheat lines (ANOVA P= 0.60 and P= 0.93). While significant variation in reactions to the resistant lines were detected, none of the lines appeared particularly resistant to Montana populations, with mean Rf values of 13.1 and 15.4 for trials 1 and trials 2, respectively. Results suggest plant parasitic nematodes are localized problems, with P. neglectus and Heterodera species of particular concern, and that "resistant" wheat lines and barley may ineffective in managing P. neglectus in some regions of the state.Item Potato and potato virus Y: the effect of cultivar, seed type, and dfense-inducing agents differences in incidence(Montana State University - Bozeman, College of Agriculture, 2016) Boyd, Elisa Kirk; Chairperson, Graduate Committee: Michelle Flenniken; Eileen Carpenter, Michelle Flenniken and Nina Zidack were co-authors of the article, 'Potato cultivar and seed type affect incidence of potato virus Y (PVY N-WI) infection' submitted to the journal 'Plant disease' which is contained within this thesis.; Eileen Carpenter, Michelle L. Flenniken and Nina Zidack were co-authors of the article, 'Examination of resistance-inducing compounds to limit potato virus Y (PVY N-WI) infection in potatoes' which is contained within this thesis.Potato (Solanum tuberosum subsp. tuberosum) is an important crop grown worldwide. Propagated vegetatively, a sustainable potato industry relies on pathogen free, tissue culture-produced plantlets to maintain low disease incidence in seed potato stock. Potato virus Y (PVY) infection is the most significant threat to seed potato production. Therefore, determining the influence of cultivar and seed type on PVY incidence could lead to improved management practices. Data from seed potato certification inspection in Montana indicated that plants grown from seed produced in sterile conditions (plantlets and minitubers) had a greater incidence of PVY than plants grown from field-produced tubers. We hypothesized that differences in cultivar, seed type and growth conditions (i.e., sterile vs. field grown) impacted PVY incidence. Systemic acquired resistance (SAR) is a plant immune response that is induced by pathogens and resistance-inducing agents. Resistance-inducing agents are effectively used to limit fungal pathogens, and we hypothesized that they may also limit PVY infection. To test these factors, potato plants (cultivars Russet Burbank and Norkotah Colorado 3) were grown from multiple seed types (i.e., plantlet, minituber, and Generation 3 tuber (G3)) and mechanically inoculated with PVY strain Wilga in the presence and absence of Systemic Acquired Resistance (SAR) inducing agents. Percent infection (incidence) was measured with double-antibody sandwich enzyme-linked immunosorbent assay (DASELISA) at three time points post-inoculation. These studies resulted in the following conclusions: (1) incidence of PVY infection varies by cultivar, specifically, the Russet Burbank cultivar had a lower incidence of PVY than the Norkotah Colorado 3 cultivar, (2) Russet Burbank plants grown from tissue culture plantlets had a higher incidence of PVY infection than Russet Burbank plants grown from field-produced G3) tubers, and (3) phosphorous acid (Phostrol®), an inducer of Systemic Acquired Resistance (SAR) may reduce PVY infection, particularly in Russet Burbank plantlets. These findings advance our understanding of the differences in PVY incidence by cultivar and seed type, and in turn provide valuable information for maintaining pathogen free potato seed.Item Breeding for root lesion nematode resistance in Montana winter wheat(Montana State University - Bozeman, College of Agriculture, 2015) May, David Bruce, III; Chairperson, Graduate Committee: Philip L. BrucknerRoot lesion nematodes (RLN; Pratylenchus spp.) present a serious challenge to dryland wheat production worldwide. Development of resistant cultivars would provide great economic benefit to growers. From 2012-2013, a set of backcross lines (MT08185//MT08184/Persia 20) was screened twice for resistance to P. neglectus. Progeny and parent lines were grown in infested soil for 16 to 18 weeks. Nematodes were then extracted from roots of individual plants and counted to obtain per plant final populations. ANOVA results from the 2013 screen showed significant differences in mean P. neglectus populations among lines (p < 0.01). The median final population of susceptible parent MT08184 was an estimated 4.9 times greater than that of resistant parent Persia 20. A 2013 field trial in the absence of root lesion nematodes indicated reductions in grain yield, volume weight, and protein were not associated with resistance. Seven RLN-resistant lines were identified in field evaluations with agronomic phenotypes for yield, volume weight and protein comparable to those of five widely-grown checks. Identification of quantitative trait loci (QTL) for resistance to RLN will facilitate marker-assisted introgression of resistance genes in a backcross-breeding program. Single-marker analysis of 218 genome-wide single nucleotide polymorphism markers (SNPs) was performed to identify genomic regions associated with resistance to P. neglectus. The analysis identified putative marker-trait associations on chromosomes 1AL, 1DS, 2BL, 5BL, 5DL, 7AL and 7DL (all p < 0.05). Overall, phenotypic screens as applied were inadequate to consistently characterize wheat lines for RLN resistance. As such, RLN resistance phenotypes and putative QTL effects identified in the study must be verified in future experiments.Item Characterization of two different genetic mechanisms involved in the rust resistance defense response in wheat(Montana State University - Bozeman, College of Agriculture, 2013) Talajoor, Mina Rachelle; Chairperson, Graduate Committee: Li Huang; Li Huang, Jesse Poland and Peng Zhang were co-authors of the article, 'MNR220 mediates pre-haustorial defense response to rusts at the seedling stage' which is contained within this thesis.; Li Huang, Xianming Chen and Yue Jin were co-authors of the article 'A stem rust suppressor on 7DL in the spring wheat cultivar canthatch' which is contained within this thesis.Wheat leaf rust, stem rust, and stripe rust are major fungal diseases of wheat caused by Puccinia triticina, P. graminis f. sp. tritici, and P. striiformis f. sp. tritici, respectively. Development of wheat varieties with genetic resistance to pathogens is a common strategy to protect against significant yield loss. However, incorporating resistance is not always straightforward, and understanding the mechanisms responsible for triggering host resistance is key. Here, were characterized two different genetic mechanisms involved in the rust resistance defense response in wheat. Two spring wheat cultivars and their respective EMS mutants, which displayed enhanced resistance to leaf, stem, and/or stripe rust, were studied. The cultivar Canthatch possesses a stem rust resistance suppressor on chromosome 7DL. We characterized the spectrum of resistance of Canthatch and the mutant CTH-NS, confirming the specificity of this suppressor is stem rust-specific. The cultivar Alpowa mutant MNR220 displays broad-spectrum resistance to a number of wheat rust races at the seedling stage. We characterized the functional resistance of MNR220 to a race of leaf rust by sampling inoculated tissues at various time points and tracking the disease progress microscopically. The mutant MNR220 confers resistance at the pre-haustorial stage; formation of haustoria is delayed or inhibited in MNR220 relative to the wild type Alpowa.Item Bacterial leaf and stem blight of safflower in Montana : its epidemiology, sources of resistance and inheritance of resistance(Montana State University - Bozeman, College of Agriculture, 1982) Jacobs, Darrel LeeItem Effect of Tagetes minuta on the plant parasitic southern root-knot nematode, Meloidogyne incognita, sugarbeet cyst nematode, Heterodera schachtii and nontarget aquatic macroinvertebrates(Montana State University - Bozeman, College of Agriculture, 1999) Kumar, AnujItem 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 The effect of the Russian wheat aphid on cold-hardiness of acclimating winter wheat seedlings(Montana State University - Bozeman, College of Agriculture, 1991) Storlie, Eric William