Sydney E Everhart

Sydney E Everhart
University of Connecticut | UConn · Plant Science and Landscape Architecture

PhD

About

67
Publications
22,897
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628
Citations
Introduction
My research interests are to better understand how and why plant disease outbreaks occur, using epidemiology, population genetics, and genomics.
Additional affiliations
August 2021 - present
University of Connecticut
Position
  • Professor (Associate)
August 2014 - August 2021
University of Nebraska at Lincoln
Position
  • Professor (Associate)
September 2012 - August 2014
Oregon State University
Position
  • PostDoc Position
Description
  • Molecular epidemiology and population genomics of Phytophthora ramorum.

Publications

Publications (67)
Article
Full-text available
The purpose of this study was to determine the fine-scale genetic structure of populations of the brown rot pathogen Monilinia fructicola within individual peach tree canopies to better understand within-tree plant pathogen diversity and to complement previous work on spatio-temporal development of brown rot disease at the canopy level. Across 3 ye...
Chapter
Full-text available
Phytophthora ramorum is a recently emerged plant pathogen and causal agent of one of the most destructive and devastating diseases currently affecting US horticulture and forests. It is now known to affect more than 100 plant species, including nursery and forest host species. Like many Phytophthora species, P. ramorum is a clonal organism and prod...
Article
Full-text available
Tree canopies are architecturally complex and pose several challenges for measuring and char-acterizing spatial patterns of disease. Recently devel-oped methods for fine-scale canopy mapping and three-dimensional spatial pattern analysis were applied in a 3-year study to characterize spatio-temporal de-velopment of pre-harvest brown rot of peach, c...
Article
Full-text available
Characterization of spatial patterns of plant disease can provide insights into important epidemiological processes such as sources of inoculum, mechanisms of dissemination, and reproductive strategies of the pathogen population. Whilst two-dimensional patterns of disease (among plants within fields) have been studied extensively, there is limited...
Article
Full-text available
Rapid evolution of fungal pathogens poses a serious threat to medicine and agriculture. The mutation rate determines the pace of evolution of a fungal pathogen. Hypermutator fungal strains have an elevated mutation rate owing to certain defects such as those in the DNA mismatch repair system. Studies in Saccharomyces cerevisiae show that hypermutat...
Article
Full-text available
DNA barcoding with the mitochondrial COI gene reveals distinct haplotype subgroups within the monophyletic and parthenogenetic nematode species, Mesocriconema xenoplax . Biological attributes of these haplotype groups (HG) have not been explored. An analysis of M. xenoplax from 40 North American sites representing both native plant communities and...
Chapter
Definitions of myxomycete terminology used in species descriptions are provided and include those relating to the morphology of fruiting bodies, occurrences in habitats, and biology associated with life cycle stages. These definitions include illustrations of fruiting bodies and structural parts along with publications and page numbers to guide the...
Article
The goal of this research was to advance the foundational knowledge required to quantify and mitigate fungicide resistance in Rhizoctonia zeae, the seedling disease pathogen of soybean and corn. In vitro sensitivity to azoxystrobin, fludioxonil, sedaxane, and/or prothioconazole was determined for 91 R. zeae isolates obtained mostly from soybean and...
Article
Monilinia fructicola, causal agent of brown rot of stone fruits, is an economically important problem worldwide. Six of the sequence tagged microsatellite sites developed for M. fructicola were used to genotype 68 M. fructicola isolates, which included isolates from three cities in Turkey (n = 42) that were compared to isolates from the USA (n = 15...
Article
Stress from exposure to sublethal fungicide doses may cause genomic instability in fungal plant pathogens, which may accelerate the emergence of fungicide resistance or other adaptive traits. In a previous study, five strains of Sclerotinia sclerotiorum were exposed to sublethal doses of four fungicides with different modes of action, and genotypin...
Article
Full-text available
Managed honey bees (Apis mellifera L.) and wild bees provide critical ecological services that shape and sustain natural, agricultural, and urban landscapes. In recent years, declines in bee populations have highlighted the importance of the pollination services they provide and the need for more research into the reasons for global bee losses. Sev...
Article
Cover crop fall biomass production and thus successful provisioning of ecosystem services depend on the previous cash crop harvest date. We used a process-based eco-physiological model to investigate the potential of short-season soybean maturity groups (MG) to lengthen the cover crop growing window while achieving yields similar to full-season MG...
Article
Full-text available
Accelerating the pace of microbiome science to enhance crop productivity and agroecosystem health will require transdisciplinary studies, comparisons among datasets, and synthetic analyses of research from diverse crop management contexts. However, despite the widespread availability of crop-associated microbiome data, variation in field sampling a...
Article
Full-text available
Cover crops (CC) have been explored in corn (Zea mays L.), cotton (Gossypium hirsutum L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) systems for their allelopathic potential to control weeds. However, allelopathic compounds may negatively affect these row crops by reducing germination, emergence, and grain yields. We review...
Article
Rhizoctonia solani AG-2-2IIIB is an important seedling pathogen of soybean in North America and other soybean-growing regions around the world. There is no information regarding the population genetics of field populations of R. solani associated with soybean seedling disease. More specifically, information regarding genetic diversity, the mode of...
Article
Full-text available
Invasive alien species often have reduced genetic diversity and must adapt to new environments. Given the success of many invasions, this is sometimes called the genetic paradox of invasion. Phytophthora ramorum is invasive, limited to asexual reproduction within four lineages, and presumed clonal. It is responsible for sudden oak death in the Unit...
Article
White mold (or Sclerotinia stem rot), caused by Sclerotinia sclerotiorum, is a yield-reducing disease of great importance to both dry bean and soybean crops in the Americas. Characterization of both the physiological resistance in commercial cultivars to white mold disease and the range of aggressiveness among S. sclerotiorum isolates collected fro...
Article
The clonal, necrotrophic plant pathogen, Sclerotinia sclerotiorum is the causal agent of white mold on soybean, which causes significant losses for Brazilian farmers each year. While assessments of population structure and clonal dynamics can be beneficial for determining effective management strategies, few studies have been performed. In this pap...
Article
Mycelial compatibility, the ability for fungal isolates to grow together and form one single colony, was defined for Sclerotinia sclerotiorum nearly 30 years ago and has since been used as a marker to describe clonal variation in population genetic studies. While evidence suggests an associative relationship between mycelial compatibility and veget...
Article
Full-text available
Crataegus, is a genus classified in family Rosaceae and includes several tree species commonly called Tejocote that are widely cultivated for their pome fruits in Mexico. During fall of 2014, 2015, and 2016, severe symptoms of anthracnose were observed on approx. 60% of tejocote (Crataegus gracilior) fruits in an orchard located in Tulancingo, Oaxa...
Preprint
Full-text available
Mycelial compatibility, the ability for fungal isolates to grow together and form one single colony, was defined for Sclerotinia sclerotiorum nearly 30 years ago and has since been used as a marker to describe clonal variation in population genetic studies. While evidence suggests an associative relationship between mycelial compatibility and veget...
Preprint
Full-text available
Mycelial compatibility, the ability for fungal isolates to grow together and form one single colony, was defined for Sclerotinia sclerotiorum nearly 30 years ago and has since been used as a marker to describe clonal variation in population genetic studies. While evidence suggests an associative relationship between mycelial compatibility and veget...
Preprint
Full-text available
Sclerotinia sclerotiorum (Lib.) de Bary is an important yield-reducing disease in the United States and Brazil with a diverse host range, including dry bean and soybean. Characterization of both the physiological resistance of commercial cultivars to S. sclerotiorum and the range of aggressiveness among S. sclerotiorum isolates collected from locat...
Preprint
Full-text available
Sclerotinia sclerotiorum (Lib.) de Bary is an important yield-reducing disease in the United States and Brazil with a diverse host range, including dry bean and soybean. Characterization of both the physiological resistance of commercial cultivars to S. sclerotiorum and the range of aggressiveness among S. sclerotiorum isolates collected from locat...
Preprint
Full-text available
The clonal, necrotrophic plant pathogen, Sclerotinia sclerotiorum is the causal agent of white mold on soybean, causing significant losses for Brazilian farmers each year. While assessments of population structure and clonal dynamics can be beneficial for determining effective management strategies, few studies have been performed. In this paper, w...
Preprint
Full-text available
The clonal, necrotrophic plant pathogen, Sclerotinia sclerotiorum is the causal agent of white mold on soybean, causing significant losses for Brazilian farmers each year. While assessments of population structure and clonal dynamics can be beneficial for determining effective management strategies, few studies have been performed. In this paper, w...
Article
Full-text available
The causal agents of apple bull’s-eye rot in southern Brazil have recently been described as Neofabraea actinidiae and N. brasiliensis. Isolates of both species were evaluated for response of mycelial growth index (MGI) to different temperatures, enzyme production, mycelial growth inhibition and effective concentrations (EC50 and EC100) of the fung...
Article
Full-text available
The ascomycete pathogen Sclerotinia sclerotiorum is a necrotrophic pathogen on over 400 known host plants, and is the causal agent of white mold on dry bean. Currently, there are no known cultivars of dry bean with complete resistance to white mold. For more than 20 years, bean breeders have been using white mold screening nurseries (wmn) with natu...
Preprint
Full-text available
The ascomycete pathogen Sclerotinia sclerotiorum is a necrotrophic pathogen on over 400 known host plants, and is the causal agent of white mold on dry bean. Currently, there are no known cultivars of dry bean with complete resistance to white mold. For more than 20 years, bean breeders have been using white mold screening nurseries with natural po...
Preprint
Full-text available
The ascomycete pathogen Sclerotinia sclerotiorum is a necrotrophic pathogen on over 400 known host plants, and is the causal agent of white mold on dry bean. Currently, there are no known cultivars of dry bean with complete resistance to white mold. For more than 20 years, bean breeders have been using white mold screening nurseries with natural po...
Preprint
Full-text available
The ascomycete pathogen Sclerotinia sclerotiorum is a necrotrophic pathogen on over 400 known host plants, and is the causal agent of white mold on dry bean. Currently, there are no known cultivars of dry bean with complete resistance to white mold. For more than 20 years, bean breeders have been using white mold screening nurseries with natural po...
Chapter
In this chapter, the definitions of myxomycete terminology used to describe species are provided and also include the morphology of fruiting bodies, occurrences in habitats, and biology associated with life cycle stages. These terms include illustrations of fruiting bodies and structural parts along with publications and page numbers to guide the u...
Article
Population genetic analysis is a powerful tool to understand how pathogens emerge and adapt. However, determining the genetic structure of populations requires complex knowledge on a range of subtle skills that are often not explicitly stated in book chapters or review articles on population genetics. What is a good sampling strategy? How many isol...
Article
Sclerotinia sclerotiorum is a necrotrophic fungal pathogen that causes white mold of dry bean (Phaseolus vulgaris L.). Chemigation with fungicides is used for disease control, but effectiveness of this application method and impact of irrigation level on residual fungicide activity in the plant over time under field conditions has not been well cha...
Article
Knowledge of pathogen population structure is useful to identify isolates for screening cultivars and lines for resistance. For S. sclerotiorum, causal agent of white mold in more than 400 plant species, including common bean and soybean, breeding for resistance is particularly challenging. The objective of this study was to characterize phenotypic...
Article
Background: Monilinia fructicola is a diverse pathogen of pome and stone fruits that causes severe economic losses each year. However, little is known about inoculum flow within or between orchards and pathogen establishment in an orchard, because few methods exist for detecting diversity or tracking isolates over time. SSR loci are an effective o...
Article
Full-text available
Pathogen exposure to sublethal doses of fungicides may result in mutations that may represent an important and largely overlooked mechanism of introducing new genetic variation into strictly clonal populations, including acquisition of fungicide resistance. We tested this hypothesis using the clonal plant pathogen, Sclerotinia sclerotiorum. Nine su...
Data
Change in EC50 of Sclerotinia sclerotiorum isolates after exposure to sub-lethal doses of fungicide for 12 generations. (DOCX)
Article
Genotyping of Sclerotinia sclerotiorum isolates exposed and non-exposed to sub-lethal fungicides.
Article
Full-text available
The aim of this study was to evaluate the temporal dynamics of downy mildew epidemics under four training systems: vertical shoot positioning (VSP), Geneva Double Curtain (GDC), Simple Curtain (SC) and Tendone in two cultivars (‘Cabernet Sauvignon’ and ‘Merlot’). Experiments were conducted at commercial vineyards in southern Brazil, during the 2012...
Article
In this study, we investigated whether fungicide-induced mutagenesis previously reported in Monilinia fructicola could accelerate genetic changes in field populations. Azoxystrobin and propiconazole were applied to nectarine trees at weekly intervals for approximately 3 months between bloom and harvest in both 2013 and 2014. Fungicides were applied...
Article
Full-text available
Development of tools to identify species, genotypes, or novel strains of invasive organisms is critical for monitoring emergence and implementing rapid response measures. Molecular markers, although critical to identifying species or genotypes, require bioinformatic tools for analysis. However, user-friendly analytical tools for fast identification...
Preprint
Development of tools to identify species, genotypes, or novel strains of invasive organisms is critical for monitoring emergence and implementing rapid response measures. Molecular markers, although critical to identifying species or genotypes, require bioinformatic tools for analysis. However, user-friendly analytical tools for fast identification...
Preprint
Full-text available
Development of tools to identify species, genotypes, or novel strains of invasive organisms is critical for monitoring emergence and implementing rapid response measures. Molecular markers, although critical to identifying species or genotypes, require bioinformatic tools for analysis. However, user-friendly analytical tools for fast identification...
Article
Multiple traditional species names for plant pathogenic fungi have been supplemented with new names that delimit formerly cryptic species. In separate instances, isolates within a species are clearly differentiated by both phylogeny and distinctive pathogenic traits and are assigned sub-specific designations. These new species names and the sub-spe...
Article
Full-text available
Repeated applications of fungicides with a single mode of action are believed to select for pre-existing resistant strains in a pathogen population, while the impact of sub-lethal doses of such fungicides on sensitive members of the population is unknown. In this study, in vitro evidence is presented that continuous exposure of Monilinia fructicola...
Article
This primer provides a concise introduction to conducting applied analyses of population genetic data in R, with a special emphasis on non-model populations including clonal or partially clonal organisms. It provides a valuable resource for tackling the nitty-gritty analysis of populations that do not necessarily conform to textbook genetics and mi...
Article
Full-text available
Three fungicide-sensitive Monilinia fructicola isolates were exposed in weekly transfers of mycelia to a dose gradient of a DMI and a QoI fungicide (azoxystrobin) in solo or mixture treatments and fungicide sensitivity as well as genetic changes were assessed. Isolates showed a faster reduction in sensitivity (higher resistance factors) to azoxystr...
Article
Full-text available
To better understand the fine-scale spatial dynamics of brown rot disease and corresponding fungal genotypes, we analyzed three-dimensional spatial patterns of pre-harvest fruit rot caused by Monilinia fructicola in individual peach tree canopies and developed microsatellite markers for canopy-level population genetics analyses. Using a magnetic di...
Article
Full-text available
Woody grapevines (Vitis spp.) are common in the deciduous forests of the southeastern United States. Their growth habit makes leaf collection challenging and polymorphic leaves make identification of species difficult. Mature grapevines can grow up to 48 cm in diameter at breast height and reach the upper canopy of trees more than 35 m in height. L...
Article
Full-text available
Myxomycetes, the true slime molds, are highlighted in research and teaching that emphasizes various stages of the life cycle as experimental models. Past and current phylogenetic classifica- tions of Myxomycetes on the tree of life are presented. Life cycle stages are illustrated, described, and discussed. Simple laboratory demonstrations and exper...
Article
Full-text available
Certain species of myxomycetes (plasmodial slime molds) are regularly present with mosses, lichens, and algae. Corticolous myxomycetes were previously studied in the tree canopy, and observations suggested that species occurrence is patchy and species abundance may increase with the presence of bryophytes and lichens. The purpose of this study was...
Article
Full-text available
Students from the University of Central Missouri explored the tree canopies of the Great Smoky Mountains National Park in Tennessee and North Carolina, Daniel Boone National Forest in Kentucky, and Big Oak Tree State Park, Ha Ha Tonka State Park, and Pertle Springs in Missouri from the summer of 2000 to 2007. The Doubled Rope Climbing Method (DRCM)...
Article
Full-text available
This paper highlights and expands on some of the major points of good taxonomic practice. Myxomycete species concepts are reviewed, monotypic genera are discussed and critiqued, and case study examples are given for Badhamiopsis ainoae, Protophysarum phloiogenum, and Trabrooksia applanata. Monotypic genera are suggested for DNA sequencing to resolv...
Article
This paper highlights and expands on some of the major points of good taxonomic practice. Myxomycete species concepts are reviewed, monotypic genera are discussed and critiqued, and case study examples are given for Badhamiopsis ainoae, Protophysarum phloiogenum, and Trabrooksia applanata. Monotypic genera are suggested for DNA sequencing to resolv...
Article
Full-text available
The myxomycete life cycle is reviewed and evaluated based on historic and current evidence, and completely illustrated in detail, including trophic stages (myxamoebae, swarm cells, and plasmodia), resting or dormant stages (spores, microcysts, and sclerotia), and developing fruiting bodies. Most books and journal papers fail to include all life cyc...
Article
This study compares the occurrence and distribution of myxomycete species in the canopy of living trees and neighboring grapevines. Corticolous myxomycetes of three temperate forests in southeastern USA were studied on six tree species (30 trees) and grapevines (30 vines) to determine distribution and occurrence of myxomycete species relating to ge...
Article
Full-text available
This study compares the occurrence and distribution of myxomycete species in the canopy of living trees and neighboring grapevines. Corticolous myxomycetes of three temperate forests in southeastern USA were studied on six tree species (30 trees) and grapevines (30 vines) to determine distribution and occurrence of myxomycete species relating to ge...
Article
Full-text available
Plasmodia, sclerotia, and fruiting bodies are stages in the myxo-mycete life cycle that are easiest to recognize in the field. These stages can be found on different substrata such as living and dead plants and animals on the forest floor and in the canopy on bark of living trees and vines. This paper describes unusual habitats of myxomycetes on li...

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Projects (2)
Project
the goal of this research is to examine viral transmission among different landscapes (urban, agricultural, roadsides and conservation parks) with and without landscape enhancements to determine whether land management practices impact viral transmission among bees.