VTechWorks Repository :: Browsing by Author "Hong, Chuanxue"

Browsing by Author "Hong, Chuanxue"

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Analyzing the structural shifts in U.S. boxwood production due to boxwood blight
Hall, Charles R.; Hong, Chuanxue; Gouker, Fred E.; Daughtrey, Margery (Horticultural Research Institute, 2021-09-01)
The purpose of this study is to examine the changes in the sales of boxwood (Buxus spp.) that have occurred in boxwood production states. We theorize that some of the shifts in production areas over the period from 2009 to 2019 have been impacted by the introduction of boxwood blight into the United States. Boxwood blight (Calonectria pseudonaviculata) was first observed in the U.S. in 2011 by plant pathologists in 8 states: Connecticut, Maryland, Massachusetts, New York, North Carolina, Oregon, Rhode Island, and Virginia. The disease has now been seen in 30 states plus the District of Columbia. The data used for this analysis is from the Census of Horticultural Specialties (CHS), a survey administered by the United States Department of Agriculture, National Agricultural Statistics Service (USDA-NASS) every five years. The findings from this analysis of the Census of Horticultural Specialties data from 2009 to 2019 indicate that there were already shifts occurring in boxwood markets prior to the introduction of boxwood blight. However, boxwood blight has exacerbated the supply chain challenges for green industry participants by limiting production in certain areas of the country, increasing the costs of producing boxwood compared to other evergreen shrubs, and perhaps dampening the demand from what might have been without the existence of the blight.
The avocado subgroup of Phytophthora citricola constitutes a distinct species, Phytophthora mengei sp. Nov.
Hong, Chuanxue; Gallegly, Mannon E.; Browne, Greg T.; Bhat, Ravindra G.; Richardson, Patricia A.; Kong, Ping (Mycological Society of America, 2009-07)
Isolates from avocado tree cankers have been recognized as a distinct subgroup within the P. citricola complex since 1974, both morphologically and molecularly (isozyme and amplified fragment length polymorphism [AFLP] analyses). This sub-group is formally separated from P. citricola after comparative DNA Fingerprinting and sequence analyses of the ITS region, as well as by morphological examinations. This new taxon is homothallic, produces plerotic oospores with paragynous antheridia and noncaducous semipapillate sporangia. Morphologically it differs from Other species of Waterhouse group III by producing many large bizarre-shaped sporangia and smaller oogonia with asymmetric capitate antheridia. It belongs to clade 2 and is phylogenetically closer to A siskiyouensis, P. capsici and P. tropicalis than to P. citricola. P. mengei can be easily differentiated from its relatives in the same clade and other species of this morpho-group by DNA fingerprints and sequence analysis. This new taxon is named Phytophthora mengei sp. nov.
Best Management Practices for Boxwood Blight for Greenery Producers
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Likins, T. Michael (Virginia Cooperative Extension, 2014-11-03)
Best management practices for boxwood blight (also called “box blight”) for greenery producers are practices recommended to avoid the introduction and spread of boxwood blight, caused by the fungus Calonectria pseudonaviculata. The recommendations in this document are designed to avoid spread of boxwood blight within a planting or to new locations when pruned tips are collected, sold and/or used for holiday greenery.
Best Management Practices for Boxwood Blight for Professionally Managed Landscapes and Public and Historic Gardens in Virginia
Bordas, Adria; Likins, T. Michael; Bush, Elizabeth A.; Dart, Norm; Hansen, Mary Ann; Hong, Chuanxue (Virginia Cooperative Extension, 2014-12-19)
Boxwood blight is caused by the fungal pathogen Calonectria pseudonaviculata(syn. Cylindrocladium buxicola). This document outlines best management practices for landscapers and property managers to reduce the risk of spreading boxwood blight to landscapes and public and historic gardens, and to manage the disease if it is introduced.
Best Management Practices for Boxwood Blight in the Virginia Home Landscape
Bush, Elizabeth A.; Hansen, Mary Ann; Dart, Norm; Hong, Chuanxue; Bordas, Adria; Linkins, T. Mike (Virginia Cooperative Extension, 2016-09)
Provides a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid the spread of the disease to new locations.
Best Management Practices for Boxwood Blight in the Virginia Home Landscape
Bush, Elizabeth A.; Hansen, Mary Ann; Dart, Norm; Hong, Chuanxue; Bordas, Adria; Linkins, T. Mike (Virginia Cooperative Extension, 2005-09-14)
Provides a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.
Best Management Practices for Boxwood Blight in Virginia Production Nurseries WITH Boxwood Blight
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Linkins, T. Mike (Virginia Cooperative Extension, 2014-07-15)
Provides a set of guidelines for production nurseries with boxwood blight to contain and manage the disease in the most effective manner and avoid the spread of the disease to new locations.
Best Management Practices for Boxwood Blight in Virginia Production Nurseries WITHOUT Boxwood Blight
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Linkins, T. Mike (Virginia Cooperative Extension, 2014-06-25)
Provides a set of guidelines for production nurseries without boxwood blight to avoid introduction of the boxwood blight pathogen into the landscape.
Best Management Practices for Boxwood Blight: Best management practices for boxwood blight in Virginia production nurseries with boxwood blight
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Likins, T. Michael (Virginia Cooperative Extension, 2014-07-15)
This Best Management Practice document is a set of guidelines for home growers of landscape boxwood to avoid introduction of the boxwood blight pathogen into a landscape or, if the disease is already present in a landscape, to manage the disease in the most effective manner and avoid spread of the disease to new locations.
Best Management Practices for Virginia Retail Nurseries WITH Boxwood Blight
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Linkins, T. Mike (Virginia Cooperative Extension, 2006-05-14)
Provides a set of guidelines for retail nurseries with boxwood blight to contain and manage the disease in the most effective manner and avoid the spread of the disease to new locations.
Best Management Practices for Virginia Retail Nurseries WITHOUT Boxwood Blight
Dart, Norm; Hong, Chuanxue; Bordas, Adria; Bush, Elizabeth A.; Hansen, Mary Ann; Linkins, T. Mike (Virginia Cooperative Extension, 2006-06-14)
Provides a set of guidelines for retail nurseries without boxwood blight to avoid introduction of the boxwood blight pathogen into the landscape.
Boxwood Blight: A New Disease of Boxwood Found in the Eastern U.S.
Dart, Norm; Hansen, Mary Ann; Bush, Elizabeth A.; Hong, Chuanxue (Virginia Cooperative Extension, 2001-12-05)
Provides information about boxwood blight so that growers can be aware of the symptoms, signs, and impacts of the pathogen and monitor nursery and landscape boxwoods for symptoms.
Boxwood phyllosphere fungal and bacterial communities and their differential responses to film-forming anti-desiccants
Li, Xiaoping; Omolehin, Olanike; Hemmings, Ginger; Tseng, Hsien T.; Taylor, Amanda; Taylor, Chad; Kong, Ping; Daughtrey, Margery; Luster, Douglas; Gouker, Fred; Hong, Chuanxue (2023-08-12)
Background Anti-desiccant is a class of agrochemicals widely used to protect plants from water stresses, rapid temperature variations, heat and sunburn, frost and freeze damages, transplant shock, and pathogen and pest attack. Although anti-desiccants are generally considered non-toxic to organisms, it is unclear whether they may impact the phyllosphere microbial communities. In this study, three film-forming anti-desiccant products, TransFilm, Vapor Gard, and Wilt-Pruf were applied to the canopy of two boxwood cultivars ‘Vardar Valley’ and ‘Justin Brouwers’ on April 13 and August 26, 2021. Shoot samples were collected from boxwood plants treated with each of the three products, as well as nontreated control on June 16, August 26 (before the second treatment), and October 18. Microbial and plant genomic DNA was isolated together and 16S rRNA gene and the extended internal transcribed spacer regions were amplified with PCR and sequenced on a Nanopore MinION platform for bacterial and fungal identification. Results Bacterial communities were more diverse than fungal communities. At the phylum level, the boxwood phyllosphere was dominated by Proteobacteria and Ascomycota; at the genus level, Methylobacterium and Shiraia were the most abundant bacteria and fungi, respectively. Among the three film-forming anti-desiccants, Vapor Gard and Wilt-Pruf had more impact than TransFilm on the microbial communities. Specifically, broader impacts were observed on fungal than bacterial community composition and structure, with most affected fungi being suppressed while bacteria promoted. Conclusion This study addressed several major knowledge gaps regarding boxwood phyllosphere microbiota and the impact of anti-desiccants on plant microbiome. We identified diverse microbial communities of boxwood, a major evergreen woody crop and an iconic landscape plant. We also found differential effects of three film-forming anti-desiccants on the composition and structure of bacterial and fungal communities. These findings advanced our understanding of the associated microbiome of this landmark plant, enabling growers to fully utilize the potentials of microbiome and three anti-desiccants in improving boxwood health and productivity.
cDNA Transcriptome of Arabidopsis Reveals Various Defense Priming Induced by a Broad-Spectrum Biocontrol Agent Burkholderia sp. SSG
Kong, Ping; Li, Xiaoping; Gouker, Fred; Hong, Chuanxue (MDPI, 2022-03-15)
Burkholderia sp. SSG is a potent biological control agent. Even though its survival on the leaf surface declined rapidly, SSG provided extended, moderate plant protection from a broad spectrum of pathogens. This study used Arabidopsis Col-0 and its mutants, eds16-1, npr1-1, and pad4-1 as model plants and compared treated plants with non-treated controls to elucidate whether SSG triggers plant defense priming. Only eds16-1 leaves with SSG became purplish, suggesting the involvement of salicylic acid (SA) in SSG-induced priming. cDNA sequencing of Col-0 plants and differential gene expression analysis identified 120 and 119 differentially expressed genes (DEGs) at 6- and 24-h post-treatment (hpt) with SSG, respectively. Most of these DEGs encoded responses to biotic and abiotic stimuli or stresses; four DEGs had more than two isoforms. A total of 23 DEGs were shared at 6 and 24 hpt, showing four regulation patterns. Functional categorization of these shared DEGs, and 44 very significantly upregulated DEGs revealed that SSG triggered various defense priming mechanisms, including responses to phosphate or iron deficiency, modulation of defense-linked SA, jasmonic acid, ethylene, and abscisic acid pathways, defense-related gene regulation, and chromatin modification. These data support that SSG is an induced systemic resistance (ISR) trigger conferring plant protection upon pathogen encounter.
Characterization of Phytophthora Species in Recycled Irrigation Water at a Container Nursery in Southwestern Virginia
Bush, Elizabeth A. (Virginia Tech, 2002-05-03)
The potential of increasing disease problems through the use of recycled irrigation water in horticultural operations is a serious concern, yet basic research on waterborne plant pathogens in Virginia is lacking. In this work seasonal fluctuations and locations of Pythiaceae in a recycled water irrigation system at a container nursery were determined. Pythium spp. were recovered more frequently and in greater numbers than Phytophthora spp. Species of Phytophthora recovered in filtering assays were identified as P. capsici, P. citricola, P. citrophthora, P. cryptogea, P. drechsleri, and P. nicotianae. P. cryptogea and P. drechsleri were the only Phytophthora spp. recovered from baits placed on the surface of the irrigation reservoir, whereas a greater diversity of species was recovered from baits placed at depths. Hymexazol-amended medium was found to have limitations in recovery of Phytophthora spp. In pathogenicity tests, P. cactorum, P. capsici, P. citrophthora, and P. nicotianae caused significant mortality of Salvia officinalis and P. cactorum showed limited pathogenicity on Gerbera jamesonii. Asymptomatic (aboveground) plants were found to harbor inoculum long after Phytophthora-inoculation. Fresh weight analyses of roots and shoots of asymptomatic plants demonstrated that Phytophthora inoculation may either reduce or stimulate plant shoot growth, but little effect is apparent on roots. Irrigation with naturally infested irrigation water reduced plant growth. This research provides data for prioritizing development of detection technology and management practices for plant pathogens in irrigation water. The results may also lead to improvements in conventional water assay protocols for plant pathogens.
Characterization of Boxwood Shoot Bacterial Communities and Potential Impact from Fungicide Treatments
Li, Xiaoping; Tseng, Hsien Tzer; Hemmings, Ginger; Omolehin, Olanike; Taylor, Chad; Taylor, Amanda; Kong, Ping; Daughtrey, Margery; Gouker, Fred; Hong, Chuanxue (American Society for Microbiology, 2023-04)
Agrochemicals are important tools for safeguarding plants from invasive pathogens, insects, mites, and weeds. How they may affect the plant microbiome, a critical component of crop health and production, was poorly understood. Phyllosphere bacterial communities play important roles in plant fitness and growth. The objective of this study was to characterize the epiphytic and endophytic bacterial communities of boxwood shoots and determine how they may respond to commonly used fungicides. In early summer and early fall, shoot samples were collected immediately before and 1, 7, and 14days after three fungicides containing chlorothalonil and/or propiconazole were applied to the canopy. Total genomic DNA from shoot surface washings and surface-sterilized shoot tissues was used as the template for 16S rRNA metabarcoding, and the amplicons were sequenced on a Nanopore MinION sequencer to characterize the epiphytic and endophytic communities. The bacterial communities were phylogenetically more diverse on the boxwood shoot surface than in the internal tissue, although the two communities shared 12.7% of the total 1,649 identified genera. The most abundant epiphytes were Methylobacterium and Pantoea, while Stenotrophomonas and Brevundimonas were the dominant endophytes. Fungicide treatments had strong impacts on epiphytic bacterial community structure and composition. Analysis of compositions of microbiomes with bias correction (ANCOM-BC) and analysis of variance (ANOVA)-like differential expression (ALDEx2) together identified 312 and 1,362 epiphytes changed in abundance due to fungicide treatments in early summer and early fall, respectively, and over 50% of these epiphytes were negatively impacted by fungicide. The two chlorothalonil-based contact fungicides demonstrated more marked effects than the propiconazole-based systemic fungicide. These results are foundational for exploring and utilizing the full potential of the microbiome and fungicide applications and developing a systems approach to boxwood health and production. IMPORTANCE Agrochemicals are important tools for safeguarding plants from invasive pathogens, insects, mites, and weeds. How they may affect the plant microbiome, a critical component of crop health and production, was poorly understood. Here, we used boxwood, an iconic low-maintenance landscape plant, to characterize shoot epiphytic and endophytic bacterial communities and their responses to contact and systemic fungicides. This study expanded our understanding of the above-ground microbiome in ornamental plants and is foundational for utilizing the full benefits of the microbiome in concert with different fungicide chemistries to improve boxwood health. This study also sets an example for a more thorough evaluation of these and other agrochemicals for their effects on boxwood microbiomes during production and offers an expanded systems approach that could be used with other crops for enhanced integrated pest management.
Characterization of the Soil Bacterial Community from Selected Boxwood Gardens across the United States
Li, Xiaoping; Kong, Ping; Daughtrey, Margery; Kosta, Kathleen; Schirmer, Scott; Howle, Matthew; Likins, Michael; Hong, Chuanxue (MDPI, 2022-07-26)
In a recent study, we observed a rapid decline of the boxwood blight pathogen Calonectria pseudonaviculata (Cps) soil population in all surveyed gardens across the United States, and we speculated that these garden soils might be suppressive to Cps. This study aimed to characterize the soil bacterial community in these boxwood gardens. Soil samples were taken from one garden in California, Illinois, South Carolina, and Virginia and two in New York in early summer and late fall of 2017 and 2018. Soil DNA was extracted and its 16S rRNA amplicons were sequenced using the Nanopore MinION^® platform. These garden soils were consistently dominated by Rhizobiales and Burkholderiales, regardless of garden location and sampling time. These two orders contain many species or strains capable of pathogen suppression and plant fitness improvement. Overall, 66 bacterial taxa were identified in this study that are known to have strains with biological control activity (BCA) against plant pathogens. Among the most abundant were Pseudomonas spp. and Bacillus spp., which may have contributed to the Cps decline in these garden soils. This study highlights the importance of soil microorganisms in plant health and provides a new perspective on garden disease management using the soil microbiome.
Characterization, development of a field inoculation method, and fungicide sensitivity screening of the Pythium blight pathogen of snap bean (Phaseolus vulgaris L.)
Harrison, Leigh Ann (Virginia Tech, 2011-03-08)
New Jersey, Georgia, and the Eastern Shore of Virginia (ESV) are important snap bean (Phaseolus vulgaris L.) growing regions, but profitability is threatened by Pythium blight. Causal agents of Pythium blight on snap bean were identified using morphological characterization and sequence analysis of the rDNA-internal transcribed spacer (ITS) regions of 100 isolates. Most isolates were Pythium aphanidermatum (Edson) Fitzp. (53%), and also included Pythium deliense Meurs (31%; all from Georgia), Pythium ultimum Trow (12%), Pythium myriotylum Drechsler (2%), Pythium catenulatum Matthews (1%), and unknown Pythium sp. (1%). To our knowledge, this is the first report of P. deliense in Georgia and on common bean and squash (Cucurbita pepo L.); as well as the first report of P. catenulatum on lima bean (Phaseolus lunatus L.) and in New Jersey. Fungicide labeling and cultivar selection for Pythium blight management is hindered by difficulties associated with conducting successful trials, because the disease occurs sporadically and clustered in the field. Three P. aphanidermatum-infested inoculum substrates were evaluated at three concentrations. The vermiculite/V8 juice (5:3 weight to volume) inoculum (10,000 ppg/0.3 m) consistently caused at least 50% disease in 3 field trials. Sensitivity of the Pythium blight pathogens was determined in vitro against five fungicides. Twenty-two Pythium isolates representing P. aphanidermatum, P. deliense, P. ultimum, and P. myriotylum were inoculated to media amended with each active ingredient at 0, 100μg/ml, the concentration equivalent to the field labeled rate if applied on succulent beans at 187 L/ha, and the equivalent if applied at 374 L/ha. All isolates were completely sensitive (100% growth reduction, or GR) to all active ingredients at the labeled rates, except azoxystrobin. At 100μg/ml azoxystrobin, one P. deliense isolate had 8.9% GR. All isolates had 100% GR to copper hydroxide at 100μg/ml, and the lowest GR on mefenoxam-amended medium was 91.9%. At 100μg/ml cyazofamid, all P. deliense isolates were completely sensitive and variation was observed in P. aphanidermatum isolates. At 100μg/ml potassium phosphite, significant GR similarities were recorded within isolates of the same species, and less than 50% GR was observed in all P. deliense isolates.
Characterizing resistance of Erysiphe necator to fungicides belonging to the quinone outside inhibitors and demethylation inhibitors
Rallos, Lynn Esther E. (Virginia Tech, 2013-01-21)
Practical resistance of Erysiphe necator to quinone outside inhibitors (QoIs) is now widespread, and resistance to demethylation inhibitors (DMIs) has also developed. The goal of this research was to characterize fungicide resistance by elucidating resistance mechanisms and determining its stability. QoI resistance persisted for several years in a field population after QoI application ended. Resistant isolates were highly competitive in mixed populations in competition assays under laboratory conditions, indicating a lack of fitness cost. In one competition trial under field conditions, resistance frequency declined, possibly due to spore migration and influx of background inoculum, but in a second trial, it did not decline. Double resistance to QoI and DMI was detected and DMI application may have been partially responsible for maintaining QoI resistance in the field. One isolate with QoI resistance but an undetectable level of the major QoI mutation was shown to be heteroplasmic -- resistant strains could be selected from this isolate. DMI resistance mechanisms in E. necator included the Y136F mutation in CYP51 and cyp51 over-expression. The first mechanism was present in almost all isolates with substantial levels of resistance, and cyp51 expression level was correlated with resistance level. Three cyp51 genotypes were detected. Wildtype isolates with the TAT genotype were sensitive to DMIs, while isolates with increased resistance had either a TTT or TWT genotype; TWT indicated the presence of both wildtype and mutant alleles. Cyp51 was expressed 1.4 to 19 times more in mutants than in wildtype. It is not known whether the significant differences in cyp51 expression level among isolates and among genotype groups are due to gene copy number variation. DMI resistance was found to decline after years of subculturing, and the decline appeared to occur after a few culture transfers of field samples on fungicide-free host leaves. The observed decline, together with the finding that isolates could be "trained" to increase resistance, and may be slightly induced in cyp51 expression when successively challenged to grow in increasing fungicide concentration, indicate instability of DMI resistance.
Combating an Invasive Boxwood Pathogen - Calonectria pseudonaviculata - in the United States by Shifting Production to Less Susceptible Cultivars
Omolehin, Olanike; Keller, John; Gouker, Fred Edward; Daughtrey, Margery Louise; Luster, Douglas G.; Pscheidt, Jay W.; Hong, Chuanxue (Scientific Societies, 2022-12-08)
Boxwood Blight (BB) caused by Calonectria pseudonaviculata (Cps) is an economically devastating disease affecting the entire boxwood supply chain from growers to gardeners, since it was first officially documented in the United States in 2011. This disease has taken a heavy toll on boxwood, an iconic landscape plant and the number one evergreen nursery crop. The objective of this study was to examine the adoption of one sustainable management strategy available to growers: shifting boxwood production from highly susceptible to less susceptible cultivars. We investigated the ongoing shift by comparing boxwood sales of 17 selected nurseries from seven states across the country in 2011, 2016 and 2021. Results revealed that from 2021 to 2016, sales of cultivars highly susceptible to BB were reduced by over 35% while less sales of less susceptible boxwood cultivars increased 55%. Increased boxwood sales have been seen for 'Winter Gem', 'Wintergreen', 'SB 300' (Freedom®), 'SB 108' (Independence®), and 'Little Missy', all of which have been rated less susceptible than B. sempervirens 'Suffruticosa' in numerous trials. The potential for long-term positive impact on sustainable boxwood production and plantings in the U.S. through the use of such less susceptible cultivars is discussed. Better boxwood cultivar choices will build crop health into new plantings and sustain customer demand for boxwood. This is a case study for how sustainable crop protection strategy helps to maintain production of a crop under serious pressure from an invasive pathogen.