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Characterization and testing of reduced height (RHT) hypomorphs in durum and spring wheat
(Montana State University - Bozeman, College of Agriculture, 2023) Ugrin, Josey Mackinsey; Chairperson, Graduate Committee: Michael J. Giroux
The Reduced Height (Rht) gene in wheat (Triticum aestivum L.) increases yield by partitioning less nutrients to stem elongation and more towards spike development. In hexaploid wheat, the mutations Rht-B1b and Rht-D1b, create high-yielding semi-dwarf varieties. While Rht-B1b and Rht-D1b have been widely adopted due to their ability to increase yield, they also have drawbacks such as smaller seed size and lower protein content. Furthermore, tetraploid durum wheat (Triticum. turgidum L), Rht-B1b creates plants that are shorter than in hexaploid wheat under Northern Great Plains growing conditions. This project aimed to further characterize Rht and to develop a plant height intermediate between current standard-height and semi-dwarf varieties to increase yield in both durum and spring wheat. To create novel Rht alleles, seeds were mutagenized with Ethyl-methanesulfonate (EMS) and mutations were identified. Near-isogenic lines (NILS) were developed for the two Rht-A1 alleles and Rht-B1b-E529K alleles in semi-dwarf (Rht-B1b) and standard height (Rht-B1a) varieties in durum. In spring wheat, NILs were developed for eight Rht-A1 alleles in two high-yielding Montana varieties. These NILS were planted in field trials and plant height and grain traits were measured. Four novel mutations, Rht-A1-E63K, Rht-A1-Q6*, Rht-A1-V55M, and Rht-A1-53T in spring wheat and two mutations in durum, Rht-B1b-E529K and Rht-A1-S50F all had either significantly changed height or grain traits. Along with developing and testing Rht alleles for field trait improvement, we did a study to characterize an Rht stop-codon dosage response in wheat. Previous studies in rice and barley have indicated that a lack of the functional SLR1/SLN1 gene respectively, results in an abnormal growth response characterized by taller height and slender appearance. This effect on Rht function has yet to be tested in wheat. Rht nonsense alleles were created by screening an EMS treated population created using seed of a standard-height Montana variety. We combined mutations creating lines homozygous for single, double, or triple mutations. In field trials, Rht triple mutants exhibited a slender, elongated phenotype with strike heads similar to SLN1 mutants in barley. Differences in height varied for the other crosses but did trend towards increased height with increased Rht-stop mutation dosage.
Spatial patterns in soil depth and implications for offseason nitrogen dynamics in dryland wheat systems of central Montana
(Montana State University - Bozeman, College of Agriculture, 2022) Fordyce, Simon Isaac; Co-chairs, Graduate Committee: Clain Jones and Craig Carr; Pat Carr, Clain Jones, Jed Eberly, Scott Powell, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Exploring relationships between soil depth and multi-temporal spectral reflectance in a semi-arid agroecosystem: effects of spatial and temporal resolution' submitted to the journal 'Remote Sensing of environment' which is contained within this thesis.; Pat Carr, Clain Jones, Jed Eberly, Rob Payn, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Spatiotemporal patterns of nitrogen mineralization in a dryland wheat system' submitted to the journal 'Agriculture, ecosystems, and environment' which is contained within this thesis.
Shallow soils (< 50 cm) under dryland wheat (Triticum aestivum L.) production lose large amounts of inorganic nitrogen (N) to leaching. Crops grown in shallow soils may be more responsive to N fertilizer due to lower fertilizer recovery and suppressed mineralization, raising questions as to whether standard practices of N fertilizer rate determination can increase risks of leaching and groundwater contamination in these environments. Mineralized N can be a major nutritional supplement for wheat crops in dryland agroecosystems, so accurate estimates of mineralization inputs can have important economic and environmental implications. To assess the potential for suppressed N mineralization in shallow soils, we used spectral reflectance from up to three sensors (unmanned aerial vehicle, National Agricultural Imagery Program, and Sentinel 2) to spatially characterize soil depth on three fields in Central Montana (Chapter 2) and compared surface (0-20 cm) carbon and N cycling indices across soil depth classes (Chapter 3). Carbon dynamics were stable across depth classes while N mineralization was lower in the shallow class. Results confirm multispectral imagery as a valuable tool for non-destructively characterizing fine-scale spatial patterns in soil depth and corroborate previous findings of lower N mineralization in shallow soil environments. Given the potential for heightened fertilizer responsiveness due to lower mineralization in these environments, decision support systems for site-specific fertility management (e.g., variable rate fertilizer application) should assess the environmental consequences of leaching alongside the economic benefits of applied fertilizer rates which maximize responses of yield, quality and same-year net revenue.
Genetics of seed dormancy in wheat and barley
(Montana State University - Bozeman, College of Agriculture, 2020) Vetch, Justin Michael; Chairperson, Graduate Committee: Michael J. Giroux; Robert N. Stougaard, John M. Martin and Michael J. Giroux were co-authors of the article, 'Revealing the genetic mechanisms of preharvest sprouting' in the journal 'Plant science' which is contained within this dissertation.; Robert N. Stougaard, John M. Martin and Michael J. Giroux were co-authors of the article, 'Allelic impacts of TaPHS1, TaMKK3, and Vp1B3 on preharvest sprouting of northern Great Plains winter wheats' in the journal 'Crop science' which is contained within this dissertation.; Jason G. Walling, Jamie D. Sherman, John M. Martin and Michael J. Giroux were co-authors of the article, 'Mutations in the HvMKK3 AND HvAlaAT1 genes affect barley pre-harvest sprouting and after-ripened seed dormancy' in the journal 'Crop science' which is contained within this dissertation.; Philip L. Bruckner, John M. Martin and Michael J. Giroux were co-authors of the article, 'TAMFT homeologs are associated with preharvest sprouting winter wheat' submitted to the journal ''Crop science' which is contained within this dissertation.
Montana producers have many biotic and abiotic stresses to contend with. One of interest to avoid is preharvest sprouting (PHS), which is the precocious germination of grains before harvest. PHS affected grain is discounted at the elevator, resulting in grain being unsuitable for many foods and direct losses to producers. PHS is not widespread every year in Montana but in some years causes large economic loss. Although PHS is a response to environmental cues it is largely controlled by genetics. Genes that control seed dormancy are the most likely candidate genes for PHS resistance and the series of studies presented in this dissertation examine the impact of several genes upon small grain PHS susceptibility. The studies used several methods to assess PHS susceptibility and determine which alleles of individual genes were present. The methods included seed dormancy screening assays, alpha amylase enzyme activity analysis, falling numbers analysis, genotyping by direct sequencing and via use of various markers, RNA-sequencing, and gene expression analysis. The first study served as a PHS susceptibility survey and provides PHS tolerance information on MT grown wheat varieties. This study also found that of the three most reported PHS associated genes (TaMFT 3A, TaMKK3 4A, and TaVp1 3B), only TaMFT 3A was associated with PHS in Montana winter wheats, even though the previously reported variation was observed in all three genes. The second study looked at PHS susceptibility among current and historically grown barley varieties. It was found that malt varieties vary greatly in their susceptibility to PHS with the top grown AMBA recommended varieties among the most susceptible. It was also found that a previously unstudied mutation in the HvMKK3 gene is associated with PHS susceptibility. Interestingly, HvMKK3 and HvAlaAT1 affect dormancy at different time points in grain maturity indicating dormancy may be tailored to a specific timeframe (high dormancy at harvest with rapid decay of dormancy after harvest). The final study revisited winter wheat PHS and found that the TaMFT 3B and 3D homeologs are associated with PHS which has not been shown to date.
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.
Integrating crop diversity, forage crops, and targeted grazing to manage Avena fatua L.
(Montana State University - Bozeman, College of Agriculture, 2021) Wong, Mei-Ling; Chairperson, Graduate Committee: Fabian D. Menalled and Tim F. Seipel (co-chair)
Wild oat (Avena fatua L.) is one of the most difficult weeds to manage in spring cereal crops and causes large economic losses throughout the Northern Great Plains. The continual use of herbicides for wild oat management has selected for herbicide resistant and multiple herbicide resistant biotypes and has left no selective herbicide options for farmers in small-grain fields. To sustain crop production, this thesis aimed to develop ecologically based practices to manage wild oat populations. We evaluated the impact of spring wheat height, seeding rate, crop type, forage termination method, and tillage on wild oat tiller density, biomass, and seed production. Two studies were conducted: (1) from 2017 through 2019 in Bozeman, Montana and (2) from 2018 through 2019 in Moccasin, Montana. The first study examined the combined effect of spring wheat height and seeding rate on its competitiveness against wild oat. We found that the tall near-isogenic wheat line did not have greater wild oat suppression than the short line. Spring wheat seeded at a higher than recommended rate reduced wild oat biomass and seed production only when nitrogen fertilizer was applied. The second study assessed management practices including integrating lentil, fall and spring forage mixture, sheep grazing and tilled fallow, in addition to spring wheat height and seeding rate. Forage mixtures, sheep grazing, and tillage were the most successful tactics in suppressing wild oat growth and seed production. However, wild oat suppression was not different between spring wheat and lentil, regardless of spring wheat height and seeding rate. Our results indicate that spring wheat height was not correlated with increased suppression of wild oat. A higher seeding rate of spring wheat also did not increase wild oat suppression; we suggest that fertilization may be needed to enhance crop competitiveness. Integrating forage crops with sheep grazing has the best potential to reduce the wild oat seed bank. This information can help redesign cropping systems. However, there is a continual need to develop other integrated weed management techniques to limit wild oat growth and seed production and to reduce reliance on herbicides.
Assessment of host selection behaviors and oviposition preferences of Cephus cinctus Norton (Hymenoptera: Cephidae) using wheat and smooth brome
(Montana State University - Bozeman, College of Agriculture, 2020) Bhandari, Rekha; Chairperson, Graduate Committee: David K. Weaver and Tracy M. Sterling (co-chair)
Wheat stem sawfly, Cephus cinctus Norton (WSS), is an important pest of cereal crops in Northern Great Plains. Smooth brome has historically been suggested as a potential trap crop around wheat fields in Montana. The objective of this study was to compare oviposition preference and selection behaviors of female WSS and measure subsequent larval survival in wheat and smooth brome stems. We compared infestation, parasitism and larval development of WSS using field transects in smooth brome and adjacent wheat fields. We found no clear difference in infestation between the two host plants. There was greater larval mortality and less tunneling in smooth brome stems compared to wheat at a site near Big Sandy, Montana. At a second site near Big Sandy, there was greater infestation in smooth brome compared to wheat, but there were more dead larvae and greater parasitism in smooth brome. In Y-tube olfactometer studies, WSS females were more attracted to volatiles emitted by smooth brome than wheat. In greenhouse trials, the observation of specific behaviors leading to oviposition indicated differences in duration of ovipositor insertion and in number of ovipositor insertions that favored greater oviposition in smooth brome, but only by emergence of the first awn of the inflorescence (Zadoks 49 growth stage). There were different numbers of eggs in smooth brome stems relative to wheat, with no difference in the proportion of infested stems in choice tests conducted for two days at Zadoks 49. In no-choice tests, there were differences in both infested stems and in the number of eggs in stems at Zadoks 49. We found significantly greater amounts of key behaviorally active compounds used by female WSS, like (Z)-3-hexenyl acetate and beta-ocimene, that were among the few differences in the amounts of volatile compounds collected from two plant species. The greater amount of these compounds leads to more eggs that subsequently experience greater larval mortality in young plants, resulting in fewer cut stems in mature plants. Our findings support the consideration of smooth brome for use in trap crops to improve integrated pest management strategies for WSS.
Genetic dissection of grain yield and yield component traits in hexaploid spring wheat
(Montana State University - Bozeman, College of Agriculture, 2020) Jones, Brittney Hannah; Chairperson, Graduate Committee: Michael J. Giroux; Nancy K. Blake, Hwa-Young Heo, Jay R. Kalous, John M. Martin, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Improving hexaploid spring wheat by introgression of alleles for yield component traits from durum wheat' in the journal 'Crop science' which is contained within this dissertation.; Nancy K. Blake, Hwa-Young Heo, Jay R. Kalous, John M. Martin, Deanna L. Nash, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Impact of yield component alleles from durum wheat on end-use quality of spring wheat' in the journal 'Cereal chemistry ' which is contained within this dissertation.; Nancy K. Blake, Hwa-Young Heo, John M. Martin, Jessica A. Torrion and Luther E. Talbert were co-authors of the article, 'Allelic response of yield component traits to resource availability in spring wheat' in the journal 'Theoretical and applied genetics' which is contained within this dissertation.
Hexaploid wheat accounts for 30% of global grain production, ranking in the top three major food crop species along with maize and rice. Grain yield from hexaploid wheat is an important agronomic consideration for sustainable agriculture. As the human population continues to grow and the amount of farmable land decreases it is imperative that a focus be placed on improving grain yield performance. Grain yield is a quantitative trait and as such improved performance is largely influenced by genetic variation, environment and genotype x environment interactions. Due to the quantitative nature of grain yield the mechanisms of genetic control are largely unknown. The purpose of the presented research was to genetically dissect grain yield and yield component traits in hexaploid spring wheat grown in Montana in order to leverage new understanding to improve Montana germplasm and future breeding programs. This investigation included three research aims: (i) to determine the genetic impact of introgressed durum yield component alleles on hexaploid spring wheat agronomic and end-use quality performance (Chapters 2 and 3); (ii) investigate how resource availability as simulated by plant competition and seed density impacted yield component allele response at four yield component quantitative trait loci (Chapter 4); and (iii) to better understand the mechanism of genetic control of QTn.mst-6B a quantitative trait locus associated with tiller number through high-resolution mapping (Chapter 5). This research highlights the complexity of pleotropic interaction among yield component traits and variability associated with grain yield as impacted by environment and resources availability. Results from the three aims provide a detailed investigation of single quantitative trait loci for use as novel sources of cultivar improvement and increased genetic gain as well as, a better understanding of grain yield and yield component traits.
Evaluation of wheat production practices under wheat streak mosaic disease risk and wheat stem sawfly pressure in Montana
(Montana State University - Bozeman, College of Agriculture, 2020) McKelvy, Uta; Chairperson, Graduate Committee: Mary Burrows; Monica Brelsford, Jamie Sherman and Mary Burrows were co-authors of the article, 'Susceptibility and tolerance of winter wheat, spring wheat and barley cultivars to mechanical inoculation with wheat streak mosaic virus' submitted to the journal 'Plant health progress' which is contained within this dissertation.; Peggy Lamb, Monica Brelsford and Mary Burrows were co-authors of the article, 'Impact of planting date, seeding rate and cultivar choice on spring and winter wheat productivity and profitability in Montana' submitted to the journal 'Agronomy journal' which is contained within this dissertation.; David Weaver and Mary Burrows were co-authors of the article, 'Evaluation of chemical and cultural management practices for wheat stem sawfly control and effects on beneficial insects in spring wheat in Montana' submitted to the journal 'Journal of economic entomology' which is contained within this dissertation.
Wheat (Triticum aestivum L.) is an economically important crop for Montana's agricultural industry. Wheat streak mosaic (WSM) is an important viral disease in Montana and the wheat stem sawfly (WSS; Cephus cinctus Norton) is a major insect pest in the state. Understanding these disease and pest problems and the factors that promote and suppress disease and pest pressure forms the foundation for a successful integrated pest management program. In this dissertation, we evaluate wheat production practices in Montana and provide information on the effectiveness and implications of cultural and chemical management practices in mitigating WSM disease and WSS pressure. We assessed the tolerance of popular winter wheat, spring wheat, and barley cultivars in Montana to mechanical inoculation with WSMV in field studies. Winter wheat 'Brawl CL Plus' and breeding lines CO12D922 and MTV1681 demonstrated moderate WSMV incidence and minor yield penalties under WSMV inoculation, making them suitable cultivars to be grown in high-risk environments. We investigated the effects of cultivar choice, planting date, and seeding rate on grain yield and quality parameters in field studies. Our results validated current planting date recommendations for Montana. Yield reductions were observed at planting dates later than mid-September and April for winter wheat and spring wheat, respectively. No yield increase was observed when winter wheat was planted before mid-September. No meaningful and reliable economic benefits were associated with an increase in seeding rate beyond the recommended density. We developed a WSM risk prediction model and released it as the online learning tool AWaRe ('Assessment of Wheat streak mosaic Risk'). AWaRe presents the first learning tool that integrates complex information on the dynamics underlying WSM disease and relates them to the user in an interactive way. We expect the adoption of risk assessment based WSM management practices that result in a reduced economic impact through the use of this tool. The potential of different insecticides to manage WSS damage was compared to spring wheat genotypes with varying degrees of WSS resistance. Results showed that application of the systemic insecticide Thimet-20G provided effective protection of susceptible cultivar 'Reeder,' but use of solid-stem cultivars were similarly effective.
Characterization and identification of novel reduced height (RHT-1) alleles in wheat
(Montana State University - Bozeman, College of Agriculture, 2019) Jobson, Emma Marie; Chairperson, Graduate Committee: Michael J. Giroux; M.J. Giroux, J.M. Martin, R.E. Johnston and A.J. Oiestad were co-authors of the article, 'The impact of the wheat RHT-B1B semi-dwarfing allele on photosynthesis and seed development under field conditions' in the journal 'Frontiers in plant science' which is contained within this dissertation.; M.J. Giroux, J.M. Martin and T.M. Scheider were co-authors of the article, 'The impact of the RHT-B1B, RHT-D1B, and RHT-8 wheat semi-dwarfing genes on flour milling, baking, and micronutrients' in the journal 'Cereal chemistry' which is contained within this dissertation.; M.J. Giroux, J.M. Martin and J.B. Ohm were co-authors of the article, 'RHT-1 semi-dwarfing alleles alter dough rheology by modifying gluten composition' submitted to the journal 'Cereal chemistry' which is contained within this dissertation.; M.J. Giroux, J.M. Martin and A.C. Hogg were co-authors of the article, 'Identification and molecular characterization of novel RHT-1 alleles in hard red spring wheat' submitted to the journal 'Crop science ' which is contained within this dissertation.
Since their introduction in the 1960s, the semi-dwarfing Reduced Height (Rht-1) genes in wheat have been incorporated into the majority of modern wheat varieties. Their popularity has been driven by their positive impact on yield. The two most common semi-dwarfing alleles, Rht-B1b and Rht-D1b, reduce height ~20% and increase yield ~6% compared to tall varieties. Their shorter stature makes them less susceptible to lodging under increased water and nitrogen inputs compared to tall wheat varieties. Despite their prevalence, the exact mechanism by which Rht-B1b/Rht-D1b increase yields is still unknown. Furthermore, very little research has been done to characterize their impact on bread making and end use quality. Finally, beyond Rht-B1b and Rht-D1b, there is very little allelic diversity available to wheat breeders. The objectives of this research were to investigate the impact of Rht-B1b on photosynthesis, characterize the impact of Rht-B1b/Rht-D1b on bread making and dough rheology, and to identify and test novel Rht-1 alleles created using EMS mutagenesis. In regards to photosynthesis: we found Rht-B1b reduces flag leaf photosynthetic rate (18%) and chlorophyll A content (23%) compared to the tall wildtype at anthesis. In regards to end use quality: we found Rht-B1b/Rht-D1b decrease total grain protein content (2%) but increase gluten index (21%), bake mixing time, and bake mixing tolerance compared to the tall lines. Increased gluten index and mixing time in the semi-dwarfing lines was shown to be associated with increased high molecular weight glutenins. In regards to developing novel alleles: we identified three nonsense Rht-1 alleles and characterized their impact on coleoptile length, gibberellin responsiveness, and DELLA/GID1 interaction. Further research will be needed to investigate their impact on agronomic traits and found that each abolished GID1 interaction in the absence but not the presence of Gibberellic acid. Overall this dissertation provides new insight on the impact of the semi-dwarfing alleles on wheat growth and development, wheat milling and baking properties and increases the available allelic diversity through the introduction of three new Rht-1 nonsense alleles.
Impact of nitrogen and water management to grain yield, yield components and traits, and grain quality of two contrasting wheat classes
(Montana State University - Bozeman, College of Letters & Science, 2019) Bicego Vieitez de Almeida, Breno; Chairperson, Graduate Committee: Luther E. Talbert and Jessica Torrion (co-chair); Anish Sapkota and Jessica A. Torrion were co-authors of the article, 'Differential nitrogen and water impacts on yield and quality of wheat classes' which is contained within this thesis.; Jessica A. Torrion was a co-author of the article, 'Nitrogen and water impacts on grain yield and components of different wheat classes' which is contained within this thesis.
Wheat (Triticum aestivum L.) breeders and physiologists must consider not only grain yield but also its quality. Physiological selection may be an important tool to aid breeders achieve improvements more rapidly. However, different genotypes may have distinct responses to agronomic management and environments. The relationship between those traits also may vary according to wheat class. In the present study we characterized the grain yield, yield components and traits, and quality parameters response of four hard red and four soft white spring wheat cultivars subjected to various nitrogen (N) levels and moisture regimes (stressed vs non-stressed environment) over two years. About one-third grain yield reduction from 2016 to 2017 could be attributed to heat stress. Overall, soft whites had higher grain yield than hard reds, but a stronger negative grain yield-grain protein content relationship. Considering a given year, increments in grain yield also resulted in higher grain protein in hard reds except when N was very low. The cultivar with Gpc-B1 gene for higher grain protein, had similar grain yield to its parent material and to other well adapted hard red cultivar. Vida, characterized by extended green leaf duration after heading (stay-green trait), was better adapted to water and heat stress than the rest of hard reds. Grain fill duration was an important trait especially under heat and drought stress for both wheat classes. We found that, across moisture regime environments and year, productive tiller number had consistently a direct relation with kernel number per area, which was strongly related to grain yield. During the heat and drought stressed year, kernel weight was an important yield component and had neutral relation with kernel number. Nitrogen fertilization had effect on grain yield only during the hot and dry year with irrigation, but no effect was observed under rainfed conditions for this year. Based on the lower grain protein requirement as well the lack of N effect on grain yield for the tested conditions, soft whites may be grown with lower N input than hard reds.

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