Boxwood blight: an ongoing threat to ornamental and native boxwood

Nicholas Leblanc,Jo Anne Crouch,Catalina Salgado-Salazar

doi:10.1007/s00253-018-8936-2

Abstract

Boxwood blight is an emerging disease of ornamental and native boxwood plants in the family Buxaceae. First documented in the 1990s at a single location in England, the disease is now reported throughout Europe, Asia, New Zealand, and North America. To address the growing concern over boxwood blight, ongoing research focuses on multiple biological and genetic aspects of the causal pathogens and susceptible host plants. Characterization of genetic variation among the Calonectria fungi that cause boxwood blight shows that two unique sister species with different geographic distributions incite the disease. Studies of the pathogen life cycle show the formation of long-lived survival structures and that host infection is dependent on inoculum density, temperature, and humidity. Host range investigations detail high levels of susceptibility among boxwood as well as the potential for asymptomatic boxwood infection and for other plants in the family Buxaceae to serve as additional hosts. Multiple DNA-based diagnostic assays are available, ranging from probe-based quantitative PCR assays to the use of comparative genomics to develop robust diagnostic markers or provide whole genome-scale identifications. Though many questions remain, the research that continues to address boxwood blight demonstrates the importance of applying a multidisciplinary approach to understand and control emerging plant diseases.

Highlights

Boxwood blight disease is a significant concern for the ornamental horticulture industry and is a growing threat to established landscapes and native ecosystems alike
Despite the research advances highlighted in this review, many important questions about boxwood blight remain unanswered
Very little is known about the molecular mechanisms underlying the interaction between susceptible hosts in the family Buxaceae and fungi in the genus Calonectria that cause boxwood blight

Summary

Introduction

Boxwood blight disease ( known as box blight or buxus blight) is a significant concern for the ornamental horticulture industry and is a growing threat to established landscapes and native ecosystems alike. These findings support the idea that by manipulating the microsclerotial environment, either through direct removal of infested plant parts or leaf litter, or by introducing conditions that induce or accelerate microsclerotial mortality, pathogen survival and levels of primary inoculum could be reduced Both moisture and temperature significantly influence symptom development and the fitness of the boxwood blight pathogens (Avenot et al 2017; Gehesquière 2014; Henricot 2006). Recent work made use of whole genome scale comparisons among individual isolates to account for all possible sources of variation among isolates collected from lesions of symptomatic boxwood and sarcococca plants residing in the same landscape bed (Malapi-Wight et al 2016b) Another approach for detection under development targets proteins produced by the pathogen, rather than nucleotide sequences (Veltri et al 2016). Protein-based pathogen identification tools can be translated into field deployable, user-friendly immunological diagnostic assays for detecting the causal agents of boxwood blight

Future research and concluding thoughts

Findings

Compliance with ethical standards