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The Effects Of Ericoid Inoculum Source And Nutrient Addition On Growth And Reproduction In Highbush Blueberry, Ilana Williams

Graduate College Dissertations and Theses

Ericoid mycorrhizal fungi (EMF) form symbiotic relationships with ericaceous plants such as Vaccinium corymbosum, or highbush blueberry and assist in nutrient acquisition. EMF help plants thrive in stressful environments by increasing the area in which roots can uptake water and nutrients. In plant-mycorrhizal symbioses, nutrient uptake may depend on the identity of the fungal partner. Therefore, differently sourced mycorrhizal fungi could show differences in nutrient uptake ability. Here, I hypothesized that inoculation of V. corymbosum with EMF would enhance plant growth and investment in reproduction, and that effect would be more pronounced for plants in low nutrient conditions. I also …

Drought Tolerance In Native And Invasive Populations Of The Centaurea Jacea Hybrid Complex, Zoe Portlas

Graduate College Dissertations and Theses

Introduced plants face many ecological and evolutionary challenges when establishing in a new range, such as strong abiotic stressors and potentially novel selective environments. One such abiotic stress is water availability, which is a strong selective force shaping physiological and phenological traits that enable plants to tolerate or avoid drought stress. Despite the challenges of establishing in a new range, thousands of species have become invasive in recent centuries. Two hypotheses that may explain how a species is able to withstand stress in its introduced range are preadaptation, which posits that species are adapted to similar environments in their native …

Evolution Of Drought And Low Temperature Responses In Temperate Pooideae Grasses: Timings, Determinants, And Intersections, Aayudh Das

Graduate College Dissertations and Theses

Anthropogenically-mediated rises in atmospheric CO2 and global average temperatures is leading to increasingly severe drought and extreme weather events, the latter including unseasonal bouts of low and high temperatures. In order for plant breeders and conservation biologists to predict future responses to global warming, they must understand the ecological and evolutionary processes that shaped plant tolerance to stressful environments in the past. This is particularly true for grasses (Poaceae) that dominate approximately one-third of the Earth's vegetative cover, live in some of the world's harshest terrestrial environments, and are tremendously important, both ecologically and economically. One of the largest subfamily …

Exploring Mycorrhizae In Riparian Restoration To Enhance Phosphorus Mitigation And Pollinator Habitat On Unceded Territory, Jessica Ann Rubin

Graduate College Dissertations and Theses

When land degradation imperils freshwater quality, land managers can restore ecosystem functions. The premise of three published/accepted thesis chapters is that mycorrhizae can enhance water quality function of riparian buffers and pollinator habitat through diverse, native polyculture associations.

Where water quality is threatened through excess phosphorus (P) loads from agriculture, riparian buffers are considered Best Management Practices (BMPs). They intercept agricultural nutrients before reaching waterways. However, their seasonal cycles, saturation capacity, and often degraded conditions limit their ability to protect water quality. In particular, riparian buffers can transition from sinks to sources of P when agricultural practices chronically contribute P, …

Climate Responses Of Red Spruce (Picea Rubens Sarg.) And Its Associated Forest Community Along Elevational Gradients In The Northeastern United States., Brittany Verrico

Graduate College Dissertations and Theses

The composition of forest communities and the distributions of individual tree species are both strongly tied to climatic conditions through species-specific physiological tolerances to the abiotic environment. As a result, spatial and temporal variation in climate, both natural and anthropogenically induced, exert strong influence on tree species distributions and their adaptations to local conditions. In order for trees, which are sessile, to persist in a rapidly changing environment, genetic variation and/or phenotypic plasticity must be maintained to facilitate adaptive evolution. While strong local adaptation to current climate has been reported for trees sampled across broad spatial landscapes (e.g., latitude), few …

Influence Of Summer Hedging And Plant Growth Regulators On Apple Trees Grown For Hard Cider. An Evaluation Of Return Bloom, Tree Growth, And Juice Quality., Jessica A. Foster

Graduate College Dissertations and Theses

Fermented cider production has rapidly increased in the US over the last decade with an annualized growth rate of 50% between 2009 and 2014, and revenues totaling $ 2.2 billion in 2018 (Becot et al., 2016; Miles et al., 2020). Cider producers seek juice with high sugar, high acid, and phenolics that enhance ‘‘mouth feel’’ to make unique, high-quality cider. Specialty cider cultivars are selected for their juice qualities, not for their yield or ease of production. Growers have found many cider cultivars are challenging to grow due to disease susceptibility, biennial bearing, premature fruit drop, and excessive vegetative growth. …

Organic Amendments Alter Soil Hydrology And Belowground Microbiome Of Tomato (Solanum Lycopersicum), Taylor Readyhough

Graduate College Dissertations and Theses

Manure-derived organic amendments are a cost-effective tool that provide many potential benefits to plant and soil health. For example, amendment applications may increase soil fertility, improve soil structure, stimulate microbial activity, and suppress plant pathogens. Yet, responses to these applications may have unintended consequences. Inherent variability in the physical, chemical, and biological characteristics of these materials can result in inconsistent outcomes observed after their application. These differences are manifested in plant growth, soil physiochemical properties, and soil microbial community composition. Popular manure-derived organic amendments include dairy manure compost and poultry manure pellets. Dairy manure is an abundant resource on many …

Does Adding Forage Radish Enhance Winter Rye Cover Crops In Northeastern Corn Silage Systems?, Kirsten Cynthia Workman

Graduate College Dissertations and Theses

Cover crops play an important role in decreasing erosion and nutrient runoff associated with corn silage production in northern New England. Winter rye (Secale cereal L.) is the primary cover crop species used in this region. While winter rye (rye) monocultures are easily established, they can be challenging to manage in the spring, expensive to establish at recommended seeding rates, and can interfere with the planting of subsequent corn crops. We hypothesized that adding forage radish (Raphunus sativus L.) to a rye cover crop could augment fall performance and enhance the ecosystem services provided by the cover crop and allow …

A Generic Classification Of The Thelypteridaceae, Susan E. Fawcett

Graduate College Dissertations and Theses

The Thelypteridaceae is among the largest fern families, with over 1000 species, and comprises about 10% of all fern diversity. The family is cosmopolitan and most diverse near the equator, although species range as far north as Greenland and Alaska, and as far south as southern New Zealand. The generic classification of the Thelypteridaceae has been the subject of much controversy among authors. Proposed taxonomic systems have varied from recognizing more than 1000 species in the family within a single genus, Thelypteris, to systems favoring upwards of 30 genera. Insights on intrafamilial relationships have been gained from recent phylogenetic studies, …

Increasing The Agronomic And Economic Value Of Chickpea And Pea, Edward Marques

Graduate College Dissertations and Theses

Domestication has had a profound global impact on human history and a wide range of plants. Understanding the advertent and inadvertent effects of domestication on crops has been instrumental in bolstering food security efforts. For instance, by identifying and re-incorporating lost genotypic variation due to domestication, we can increase crop tolerance to biotic and abiotic stressors. With changing climatic conditions and the ever-growing human population, it has become more imperative to increase and fortify agricultural production. My dissertation addresses this topic in two agronomically important legumes: chickpea (Cicer arietinum) and pea (Pisum sativum). My research aims to increase the agronomic …

The Agronomics Of Organically Managed Legume-Grass Mixtures For Ensiled Forage Production, Allen Wilder

Graduate College Dissertations and Theses

Legume-grass mixtures are commonly grown on livestock farms in northern New England that feed high forage diets. Such farms typically ferment stored feed into silage that can be fed throughout the year. Many legumes and grass species are available for use in temperate climates and information on the yield, forage quality, and fermentation characteristics of various legume-grass combinations would help farmers make informed decisions about species selection and optimum management for their forage programs.

One obstacle to evaluating numerous forage treatments in agronomic research is the high variability in silage dry matter content. We hypothesized that a method of artificial …

Evolutionary History Of The Angiosperm Npf1 Gene Subfamily: Duplications, Retention And Functional Implications For Root Symbioses And Development, Giovanna Sassi

Graduate College Dissertations and Theses

ABSTRACT

The success of land plants can be attributed to the evolution of beneficial associations between plant roots and soil microbes. Root-microbe mutualisms extend the range of plant nutrient acquisition delivered through the hyphal network of mycorrhiza, an ancient and widespread plant symbiosis, or by the more recent adaptive innovation of nitrogen-fixing nodule symbioses. A plant’s genetic toolkit governs its selection of beneficial symbionts and the developmental extent of these intimate interactions. However, the evolutionary origins and function for only a few symbiotic signaling components have been explored. The central aim of this dissertation is to resolve the evolutionary events …

An Environmental Approach To Food Safety Assessment Using Artisan Cheese And Fresh Produce As Model Systems, Marie Limoges

Graduate College Dissertations and Theses

This dissertation examined recently issued regulatory standards using cheese and produce as model systems. FDA's 2015 Domestic and Imported Cheese and Cheese Products Compliance Program Guidelines (CPG) E. coli standards on cheese safety, and the extent to which these standards affect domestic and imported cheese commerce, was assessed. Results from FDA's Domestic and Imported Cheese Compliance Program for samples collected between January 1, 2004 and December 31, 2006 were analyzed. Of 3,007 cheese samples tested for non-toxigenic E. coli, 76% (2,300) of samples exceeded 10/g, FDA's target for regulatory activity. In cheese samples containing E. coli levels of 10/g and …

Ecosystem Function Along An Elevational Gradient In Vermont, Emily Page Piche

Graduate College Dissertations and Theses

Living (biotic) and non-living (abiotic) factors drive the function of ecosystems across a variety of scales from the root-soil interface to the watershed. Biotic and abiotic global change pressures such as increasing temperature and invasive species are shifting how ecosystems function. Thus, exploring and understanding how these factors shape function across the landscape is an important research area. For example, climate change both directly and indirectly affects soil microbial functions – such as carbon mineralization and nitrogen transformations – through increasing activity under warming and altering inputs to the soil through species composition changes. Mountains provide a useful tool for …

Natural Selection For Disease Resistance In Hybrid Poplars Targets Stomatal Patterning Traits And Regulatory Genes., Karl Christian Fetter

Graduate College Dissertations and Theses

The evolution of disease resistance in plants occurs within a framework of interacting

phenotypes, balancing natural selection for life-history traits along a continuum of

fast-growing and poorly defended, or slow-growing and well-defended lifestyles. Plant

populations connected by gene flow are physiologically limited to evolving along a

single axis of the spectrum of the growth-defense trade-off, and strong local selection

can purge phenotypic variance from a population or species, making it difficult to

detect variation linked to the trade-off. Hybridization between two species that have

evolved different growth-defense trade-off optima can reveal trade-offs hidden in either

species by introducing phenotypic and …

Impact Of A Winter Rye Cover Crop On Edge-Of-Field Nutrient Losses And Corn Silage Production, Keegan Griffith

Graduate College Dissertations and Theses

Cover crops have the potential to reduce environmental impacts of corn production. The objective of this study was to quantify differences in nitrogen (N) and phosphorus (P) loading between corn plots with or without a winter rye cover crop (Secale cerale). Four field plots (30 x 46 m) in Chazy, NY with edge-of-field monitoring were used for the study. Two plots were randomly assigned a rye cover crop treatment and planted with a grain drill at a rate of 112 kg ha-1 after corn silage harvest in 2015 and 2016. Continuous water flows were monitored from surface runoff and tile …

Intersection Of Salt Signaling With Nodule Initiation And Maturation During Medicago Truncatula-Sinorhizobium Meliloti Symbiosis., Sanhita Chakraborty

Graduate College Dissertations and Theses

Legumes contribute significantly to sustainable agriculture because of their high protein content. This intrinsic nitrogen is the product of a mutualistic association between their roots, and a group of soil bacteria, collectively known as rhizobia. The rhizobium-legume symbiosis is a complex developmental process that involves rhizobial entry and differentiation, coupled in space and time, with the development of a root organ (the nodule) and is subject to modulation by environmental factors. Salt stress is a strong negative regulator of rhizobium-legume symbiosis, but despite its agricultural impact, the mechanism of salt regulation of rhizobium-legume symbiosis is poorly understood. This dissertation addresses …

Management Factors Influence On The Fatty Acid Content And Composition Of Forages, Caleb Goossen

Graduate College Dissertations and Theses

Demand for ruminant-derived products high in beneficial fatty acids (FA) has led to a desire to maximize the alpha-linolenic acid (ALA) and total FA (ΣFA) content of forage crops. Several management factors affect the ALA and ΣFA content of forages, including phenology, species, season, and nitrogen fertility. Yet, the influence of harvest management decisions that affect wilting time of conserved forages is under-studied. Similarly, the majority of published research regarding ALA and ΣFA content is of cool season (C3 photosynthetic) temperate perennial forage species, and not warm season (C4 photosynthetic) annual species. Sample preservation methodologies used in published research are …

Characterization Of A Novel Vps26c-Retromer Complex And Its Interaction With An Endosomal Trafficking Pathway Regulated By The Snare Vti13 In Controlling Polarized Growth And Cell Wall Organization In Arabidopsis Thaliana, Suryatapa Ghosh Jha

Graduate College Dissertations and Theses

The endosomal trafficking system is a network of highly coordinated cellular pathways that control the growth and function of cells. The coordination of secretion and endocytosis in cells is one of the primary drivers of polarized growth, where new plasma membrane and cell wall components are deposited at the growing apex. In plants, one of the cell types exhibiting polarized growth are the root hairs. Root hairs are regulated extensions of epidermal cells called trichoblasts and are essential for anchorage, absorption of water and nutrients, and plant-microbe interactions. In this thesis, I characterize a previously undescribed protein involved in retromer …

Investigating The Effects Of Ant-Hemipteran Mutualisms On The Invertebrate Community Structure And Their Host Plant, Honey Mesquite (Prosopis Glandulosa), Nabil Nasseri

Graduate College Dissertations and Theses

Ants are ubiquitous in most communities and many form opportunistic mutualisms with honeydew-producing hemipterans (e.g. treehoppers). Hemipterans excrete honeydew, a carbohydrate rich substance, that ants harvest and, in return, ants protect their honeydew-producing partners from parasitoids, predators, and competitors. Given the efficacy of tending ants in removing hemipteran antagonists, and the strong roles that ants play within their communities as predators, competitors, and seed dispersers, surprisingly little is known of the effects of ant-hemipteran mutualisms (AHM) on the invertebrate communities in which they are embedded or on the plants that host AHM. Using observational and manipulative field experiments, I examined …

Evolution Of Duplicated Han-Like Genes In Petunia X Hybrida., Beck Powers

Graduate College Dissertations and Theses

Gene duplications generate critical components of genetic variation that can be selected upon to affect phenotypic evolution. The angiosperm GATA transcription factor family has undergone both ancient and recent gene duplications, with the HAN-like clade displaying divergent functions in organ boundary establishment and lateral organ growth. To better determine the ancestral function within core eudicots, and to investigate their potential role in floral diversification, I conducted HAN-like gene expression and partial silencing analyses in the asterid species petunia (Petunia x hybrida). My results indicate duplication of HAN-like genes at the base of Solanaceae followed by expression diversification within the flower. …

Choices And Preferences Of Vermont Master Gardeners - Do Socio-Demographics Matter?, Grace Matiru

Graduate College Dissertations and Theses

ABSTRACT

This study was designed to characterize the choices, preferences and motivations of fruit and vegetable gardeners in Vermont, and to determine whether socio-demographic characteristics affect some of these choices, preferences and motivations. Using a survey of Vermont Extension Master Gardeners (EMGs), data were gathered over a 3-year period (2011-2013). The findings show most EMGs (>90%) garden in private home gardens, and the most popular vegetables grown were tomatoes, herbs, and salad greens. Beans, cucumbers and peppers sere also popular and among fruits, blueberries, apples, raspberries and strawberries were grown by over 40% of EMGs. Approximately 10% of EMG …

Fibrolytic Enzymes And Silage Inoculants To Improve The Nutritive Value Of Silage, Salvador Ordaz

Graduate College Dissertations and Theses

Ensiling is one of the most common processes used as a conservation method for forages on farms and plays an important role in farm economics. Therefore, with the aim to improve the conservation and the nutritive value of silage, the utilization of silage additives such as fibrolytic enzymes (FE) and lactic acid bacteria (LAB) inoculants has been a common on-farm practice. FE are enzymes capable of breaking down complex polysaccharides such as cellulose and hemicellulose. The latter results in an increased substrate availability for epiphytic and inoculated LAB during silage fermentation, thus promoting a higher production of organic acids such …

From Nursery To Nature: Evaluating Native Herbaceous Flowering Plants Versus Native Cultivars For Pollinator Habitat Restoration, Annie White

Graduate College Dissertations and Theses

There is growing awareness about the value of preserving and restoring floral-rich habitats for the benefit of pollinators, especially native bees. The increasing demand for native plants in pollinator habitat restoration and other ecological landscaping applications, combined with the desire for more robust and predictable plant habits, have led to the selection and breeding of native cultivars. Yet, little is known about how these cultivated varieties differ from the native species in their ability to attract and support pollinators. I compared flower visitation by all insect pollinators to 12 native herbaceous plant species and 14 native cultivars in a replicated …

Invasive Plant Ecology In Vermont: Insights From Spatial Analysis And Interactions Of Garlic Mustard (Alliaria Petiolata) With Native Plants And Invertebrates, Chenin Kathleen Limback

Graduate College Dissertations and Theses

Causes and patterns of invasive plant species establishment and success depend broadly upon their ecology, including habitat suitability and interactions with other plants and animals. Here I examine the traits and distribution of invasive plants in Vermont, using spatial analysis, laboratory and field studies. I used GIS to investigate environmental factors correlated with presence of 19 invasive plant species in Vermont campgrounds. My results support the assumption that human dispersal of invasive plant seed and stock may be more important than natural dispersal of these plant species to new sites. I also investigate in-depth the relationships of invasive herbaceous garlic …

Evolution Of Vernalization And Photoperiod-Regulated Genetic Networks In The Grass Subfamily Pooideae, Meghan Mckeown

Graduate College Dissertations and Theses

Flowering time is a carefully regulated trait that integrates cues from temperature and photoperiod to coordinate flowering at favorable times of the year. This dissertation aims to understand the evolution of genetic architecture that facilitated the transition of Pooideae, a subfamily of grass, from the tropics to the temperate northern hemisphere approximately 50 million years ago. Two traits hypothesized to have facilitated this evolutionary shift are the use of long-term low-temperature (vernalization) to ready plants for flowering, and long-day photoperiods to induce flowering. In chapter one I review literature on the regulation of grass flowering by vernalization and photoperiod, and …

Earthworms In Vermont Forest Soils: A Study Of Nutrient, Carbon, Nitrogen And Native Plant Responses, Ryan Melnichuk

Graduate College Dissertations and Theses

Anthropogenic activities surrounding horticulture, agriculture and recreation have increased dispersal of invasive earthworms. The introduction of earthworms initiates many physical and chemical alterations in forest soils previously unoccupied by earthworms. Three trials were performed to assess the effects of earthworms on soil-water dynamics, C and N and defensive/storage compound production by a native plant.

The first trial was a greenhouse experiment, performed to assess the impact of two ecologically contrasting invasive earthworm species on percolate and evaporative soil water loss. Mesocosms were constructed to simulate a typical forest Entisol commonly penetrated by the species of interest, Lumbricus terrestris and Amynthas …

Biological Indicators Of Compost-Mediated Disease Suppression Against The Soilborne Plant Pathogen Rhizoctonia Solani, Lynn Fang

Graduate College Dissertations and Theses

Compost can suppress soilborne plant pathogens that cause significant damage on globally important food crops. However, reports of plant pathogen suppression are inconsistent likely because there are no established standards for feedstock material, application rate, and maturity age upon application. Excellent results can be achieved in greenhouse trials, but field applications are much less reliable. Disease suppression occurs through the activity of biocontrol organisms (direct antagonism), and general microbial competition. Biocontrol species are hypothesized to colonize the pile during the curing phase, but single species may not be as important as microbial consortia. Substrate composition during maturation may give rise …

The Efficacy And Non-Target Impacts Of An Organic Disease Management System Containing Biostimulants Compared With Two Sulfur-Based Systems On Four Apple Cultivars In Vermont, Ann L. Hazelrigg

Graduate College Dissertations and Theses

Disease management in organic apple orchards in Vermont is focused on controlling diseases with sulfur fungicides. The objective of this two year study was to evaluate the target and non-target effects of an organic disease management system containing agricultural biostimulants compared to two sulfur-based systems on foliar and fruit diseases, pest and beneficial arthropods, tree growth, yield and fruit quality on four cultivars, `Ginger Gold', `Honeycrisp' and `Liberty' and `Zestar!'. Trees were arranged in a complete randomized design of five three-tree replications in a certified organic orchard. The two sulfur-based systems differed in the number of applications; in the third …

Comprehensive Assessment Of Organic Apple Production In Vermont: Experience From Two Orchard Systems, 2006-2013, Terence L. Bradshaw

Graduate College Dissertations and Theses

Despite substantial consumer demand and willingness to pay premium prices for organically grown fruit, apple growers in Vermont and other New England states have been slow to adopt certified organic practices. Barriers cited in the past to increased adoption of organic apple production in the region include susceptibility of traditionally grown cultivars to apple scab, lack of effective insect pest management materials, and few available effective options for fruit thinning. Recent changes in apple cultivar plantings in the region, introduction of new insect pest management materials, and advances in crop thinning justified an evaluation of organic apple production systems containing …