Poster Session: Ecology and Epidemiology - Rhizosphere

514-P

The fungal rhizosphere of boxwoods: implications for control of the blight fungus Calonectria pseudonaviculata.
J. B. HÉBERT (1), J. A. Crouch (2), L. Cornelius (2), P. Ndukwe (2), E. Ismaiel (2), L. A. Beirn (3)
(1) USDA ARS Systematic Mycology and Microbiology Laboratory / Rutgers University, Beltsville, MD, U.S.A.; (2) USDA-ARS Systematic Mycology and Microbiology Laboratory, Beltsville, MD, U.S.A.; (3) Rutgers Univ, New Brunswick, NJ, U.S.A.

Boxwood (genus Buxus) are popular landscaping and topiary plants estimated to be worth at least $103 million annually in the USA. Boxwood production is threatened by the newly emergent fungus, Calonectria pseudonaviculata, the cause of boxwood blight, a disease that can rapidly lead to plant death. Sustainable disease management may lie in the rhizosphere of boxwood, intimately linked to plant health and a potential source of fungal natural enemies of C. pseudonaviculata. In this study, we sampled soil from the rhizosphere of forty mature boxwood plants from two arboreta collections, representing twenty different species/cultivars of boxwood. DNA was used to generate metagenome ITS sequence data through 454 pyrosequencing. There was little difference in overall community diversity among arboreta, but the composition of the communities differed. Greater differences in community diversity were found among boxwood species, but differences in community composition were less pronounced. Notably, over thirty species of Trichoderma were identified from the rhizosphere samples. Cultured Trichoderma isolates made from the soil samples reduced growth of C. pseudonaviculata by as much as 99.4% in dual-culture experiments. Differences in the rhizosphere community could play an important role in the susceptibility of Buxus species and cultivars to boxwood blight, and further studies of fungal isolates may reveal additional sources of potential biocontrol.