Location: Floral and Nursery Plants ResearchTitle: Ranking resistance of Buxus cultivars to boxwood blight – an integrated analysis
Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2020
Publication Date: 6/1/2020
Citation: Kramer, M.H., Guo, H., Pooler, M.R. 2020. Ranking resistance of Buxus cultivars to boxwood blight – an integrated analysis. Journal of Environmental Horticulture. 38(2):50-55.
Interpretive Summary: Boxwood is a valuable nursery commodity, with more than 11 million plants sold in the United States each year at a market value of $126 million. However, boxwood plants are threatened by boxwood blight, a destructive disease cause by a fungal pathogen that leads to defoliation and plant death in nurseries and established landscapes. One of the best ways to combat this pathogen is to develop resistant cultivars. Multiple studies have been conducted to screen for resistance among cultivars; however, the results of these studies are sometimes inconsistent as to which cultivars are the most disease tolerant. ARS Scientists in Beltsville, MD compiled and evaluated data from several studies to produce a list of cultivars sorted by their tolerance to boxwood blight. Results will enable further development of consistent and accurate resistance screening protocols and indicate the most suitable material for developing more resistant cultivars.
Technical Abstract: Boxwood (Buxus L. spp., Buxaceae) are popular woody landscape shrubs grown for their diverse forms and broad-leaved evergreen foliage, with an estimated $126 million economic impact in the U.S. Boxwood plants grown in temperate zones worldwide are now threatened by a destructive blight disease caused by the ascomycete fungi Calonectria pseudonaviculata and C. henricotiae. While the disease can be mitigated somewhat through cultural practices and fungicides, the most sustainable long-term solution is the development of disease tolerant boxwood cultivars. Hundreds of boxwood accessions from the National Boxwood Collection at the U.S. National Arboretum were screened for tolerance using a lab-based detached leaf assay. Comparisons of these results with those of multiple other disease resistance assays indicated that results of these studies were often inconsistent regarding which cultivars were most tolerant. We compiled and evaluated data from six studies to produce a list of cultivars sorted by their tolerance to boxwood blight. Despite the diversity in materials and methods of the studies, our method of combining and analyzing many trials in this analysis was successful in finding a consistent ordering of the boxwood cultivars.