Skip to main content
ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #399160

Research Project: Evaluation and Genetic Improvement of Woody Ornamental Landscape Plants

Location: Floral and Nursery Plants Research

Title: Boxwood Epiphytic and Endophytic bacterial communities and their differential responses to systemic and contact fungicides

item LI, XIA0PING - Virginia Tech
item TSENG, HSIEN - North Carolina Department Of Agriculture
item HEMMINGS, GINGER - North Carolina Department Of Agriculture & Consumer Services
item OMOLEHIN, OLANIKE - Virginia Tech
item TAYLOR, CHAD - North Carolina Department Of Agriculture & Consumer Services
item TAYLOR, AMANDA - North Carolina State University
item KONG, PING - Virginia Tech
item DAUGHTREY, MARGERY - Cornell University
item Gouker, Fred
item HUNG, CHUANXUE - Virginia Tech

Submitted to: Microbiology Spectrum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2023
Publication Date: 2/28/2023
Citation: Li, X., Tseng, H.T., Hemmings, G., Omolehin, O., Taylor, C., Taylor, A., Kong, P., Daughtrey, M., Gouker, F.E., Hung, C. 2023. Boxwood Epiphytic and Endophytic bacterial communities and their differential responses to systemic and contact fungicides. Microbiology Spectrum.

Interpretive Summary: Agrichemicals are important tools for protecting plants from invasive pathogens, insects, mites and weeds. However, very little is known about how these chemicals may affect plant and soil microbial communities, a critical component of crop health and production. A team of scientists examined microbial communities in boxwood, an iconic landscape plant and the #1 evergreen shrub in the United States, as a model system to characterize internal and external plant bacterial communities and their responses to three commonly used fungicides. They discovered a large variety of bacterial species with strains known to have plant health- and growth-promoting and other beneficial activities, which may help explain the low maintenance nature of this landmark plant. They also found that the fungicides affected overall bacterial diversity and composition on the leaf surface (epiphytic) but not in the internal (endophytic) communities. Different fungicide treatments enriched certain predominant bacteria in both epiphytic and endophytic communities while also suppressing others in the endophytic communities. This study provides information on integrating agrichemicals into boxwood production and developing a systems approach for crop health and production.

Technical Abstract: 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. Shoot samples were collected immediately prior to, one, seven and fourteen days after plants were sprayed with three fungicide products containing chlorothalonil and/or propiconazole in early summer and early fall. DNA from shoot surface washings and washed/surface sterilized shoots were used as template for 16S rRNA metabarcoding, and the amplicons were sequenced on a Nanopore MinION® sequencer to characterize epiphytic and endophytic communities. Overall, 1,491 bacterial genera or 36 phyla were identified from the epiphyte communities, and 438 bacterial genera or 30 phyla from the endophyte communities. The epiphytic and endophytic communities had different compositions and were dominated by Methylobacterium and Brevundimonas, respectively. Further, 124 identified epiphytes and 30 endophytes were predicted to have plant growth- and health-promoting or other beneficial activities. Fungicide treatments impacted the diversity and composition of the epiphytic communities but not those of endophytic communities. The fungicide impacts on epiphytic bacterial composition were species- and chemistry-dependent. Among the affected epiphytes, Pantoea spp. and Burkholderia spp. were enhanced while Nocardioides spp. were suppressed by two fungicide products containing chlorothalonil. These results are foundational for integrating microbiome and three fungicides and utilizing both to their full potential and developing a systems approach to boxwood health and production.