Location: Foreign Disease-Weed Science Research
Project Number: 8044-22000-051-012-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2018
End Date: Aug 31, 2023
This project focuses on boxwood blight, a destructive fungal disease affecting boxwood in the U.S. and globally. The research will help us understand the effects of pathogen genotype, boxwood cultivar, environment and phenotypic variables on boxwood blight incidence and severity. The objectives are: 1. Determine how environmental variables and pathogen diversity intersect to influence disease severity and host susceptibility in the boxwood blight pathosystem. 2. Determine how latent infections and the build-up of pathogen inoculum may be influenced by pathogen or host genotype in the boxwood blight pathosystem.
Boxwood is a high value ornamental nursery crop, with U.S. production of this widely planted evergreen shrub assessed at $103 million annually. Boxwood blight is a destructive disease of boxwood caused by two fungal pathogens in the Calonectria genus. The disease was first reported in the U.S. in late 2011, and has subsequently spread throughout 27 states. Knowledge of pathogen epidemiology and the role of environmental factors on the disease cycle can provide key information that can be used for effective cultural control, and can be incorporated into statistical models for disease forecasting and risk assessment. Many basic epidemiological questions about boxwood blight remain, including fundamental questions about how different pathogen genotypes and species differ in their behavior. Of particular concern is the impact of latent, asymptomatic infections of less susceptible cultivars and other hosts in the Buxaceae family, Pachysandra and Sarcoccocca, and how these hosts affect persistence of the pathogen in the environment. This project will combine field and growth chamber experiments to test the effects of pathogen genotype, boxwood cultivar, environment and phenotypic variables such as host susceptibility, pathogen latency, virulence, and disease incidence. A standardized screening protocol will be optimized, both in the laboratory and the field. With research done under controlled conditions in the laboratory and with a broad understanding of how plants will react to a multitude of isolates, it will be easier to categorize the sources of variability seen in field studies performed in different regions of the country and thus be able to standardize such studies. Research will make use of extensive resources previously developed in each of the Cooperator laboratories, including comparative genomic datasets for the pathogen, a collection of >500 pathogen isolates, and field sites where the disease has been resident for at least five years containing plants of differing susceptibility.