The sentinel tree nursery as an early warning system for pathway risk assessment: Fungal pathogens associated with Chinese woody plants commonly shipped to Europe

Abstract

Introduction of and invasion by alien plant pathogens represents the main cause of emerging infectious diseases affecting domesticated and wild plant species worldwide. The trade in living plants is the most common pathway of introduction. Many of the alien tree pathogens recently introduced into Europe were not previously included on any quarantine lists. To help determine the potential risk of pest introduction through trading of ornamental plants, a sentinel nursery was established in Beijing, China in 2008. The sentinel nursery planting included four of the most common ornamental woody species shipped to Europe including Ilex cornuta var. fortunae, Zelkova schneideriana, Fraxinus chinensis and Buxus microphylla. Symptoms developing on these species within the sentinel nursery were detected in 2013 and consisted of necrotic spots on leaves, canker and stem necrosis, shoot blight and shoot necrosis. Fungi associated with the trees and their symptoms included Alternaria alternata detected from all hosts; Diaporthe liquidambaris and Diaporthe capsici from bark and leaf necrosis of Zelkova schneideriana; Botryosphaeria dothidea and Nothophoma quercina from stem cankers on Fraxinus chinensis and leaf necrosis on Ilex cornuta; and Pseudonectria foliicola from leaf necrosis on Buxus microphylla. Next generation sequencing analysis from asymptomatic tissues detected eighteen OTU’s at species level among which some taxa had not been previously recorded in Europe. These results clearly demonstrate that looking at trees of internationally traded species in the region of origin can reveal the presence of potentially harmful organisms of major forestry, landscape or crop trees. Results of this study also provide an indication as to how some disease agents can be introduced using pathways other than the co-generic hosts. Hence, sentinel nurseries represent one potential mechanism to address the current lack of knowledge about pests in the countries from where live plants are shipped and the threats they represent to native flora and crops in importing countries.

EU Legislation on Forest Plant Health: an Overview with a Focus on <em>Fusarium Circinatum</em>

“…Nonetheless, many newnon-native pests were previously unknown to be harmful, or even to science, and were therefore not regulated before they invaded. To address this issue, monitoring of sentinel plants in exporting countries has been proposed as a valuable tool to identify harmful organisms prior to their arrival [72,73,74]. Although several European projects (e.g.…”

Fast and reliable molecular methods to detect fungal pathogens in woody plants

“…Sentinel planting, i.e., plants native to importing country planted in exporting countries that are inspected and analyzed at regular intervals for microbial pathogen detection, is the most promising tool (Eschen et al 2019). To this end, one could imagine associating other types of "biological" sensors that have already been the subject of promising studies, such as the sentinel plantations of European species exposed in an exotic environment (Vettraino et al 2015) or sentinel nurseries of non-native species found in their non-native environment of origin (Vettraino et al 2017). This type of sentinel also makes it possible to study the pathogenic potential and the phytosanitary risk caused by these taxa identified by their bar code sequence in air trapping (Aguayo et al 2018).…”

Forewarned is forearmed: harmonized approaches for early detection of potentially invasive pests and pathogens in sentinel plantings

“…Assuming that host-parasite co-evolution of native species might not result in obvious symptom expression, a host shift to a taxonomically similar plant species in the final location of the plant may give rise to novel host-parasite interactions. Therefore, diagnostic methods that can detect endophytic or latent pathogens must be employed (Vettraino et al 2017) in addition to standardized diagnostics for symptomatic tissue. Thus, sampling must be oriented to both symptomatic and nonsymptomatic material.…”

“…as endophytes, latent infections) or on associated commodities (e.g. soil, wood packaging) (Roques et al 2015;Vettraino et al 2017). Thus, there is a need for better tools and strategies to improve early detection of potentially harmful species before they are introduced.…”

“…A sentinel plantation ("ex-patria" plantings sensu Eschen et al 2018) can be defined as a plantation of non-native plants grown in an environment and monitored to identify biotic agents that affect the growth and vitality of those plants (Roques et al 2015;Vettraino et al 2015). A sentinel nursery ("in-patria" plantings sensu Eschen et al 2018) is defined as a site where native traded plants are planted without phytosanitary treatments in their region of production (exporting country) and monitored to identify pests and pathogens which could be spread with the trade of those plants outside of their native range (Vettraino et al 2017;. In this paper, we also consider the sentinel arboretum ( Fig.…”