Early and accurate diagnosis of new plant pathogens is vital for the rapid implementation of effective mitigation strategies and appropriate regulatory responses. Most commonly, pathogen identification relies on morphology and DNA marker analysis. However, for new diseases, these approaches may not be sufficient for precise diagnosis. In this study, we used whole-genome sequencing (WGS) to identify the causal agent of a new disease affecting Sarcococca hookeriana (sarcococca). Blight symptoms were observed on sarcococca and adjacent Buxus sempervirens (boxwood) plants in Maryland during 2014. Symptoms on sarcococca were novel, and included twig dieback and dark lesions on leaves and stems. A Calonectria sp. was isolated from both hosts and used to fulfill Koch’s postulates but morphology and marker sequence data precluded species-level identification. A 51.4-Mb WGS was generated for the two isolates and identified both as Calonectria pseudonaviculata. A single-nucleotide polymorphism at a noncoding site differentiated between the two host isolates. These results indicate that the same C. pseudonaviculata genotype has the ability to induce disease on both plant species. This study marks the first application of WGS for fungal plant pathogen diagnosis and demonstrates the power of this approach to rapidly identify causal agents of new diseases.
Ten muskmelon (Cucumis melo L.) cultivars were tested for their susceptibility to bacterial wilt, caused by Erwinia trucheiphila (Smith) Bergey, Harrison, Breed, Hammer and Huntoon and vectored by the striped cucumber beetle Acalymma vittatum (F). `Superstar', `Rising Star', `Pulsar', `Caravelle', `Cordele', `Legend', `Makdimon', `Galia', `Rocky Sweet', and `Passport' were used in field studies to determine the number of striped cucumber beetles, feeding damage, and incidence of bacterial wilt. `Makdimon' and `Rocky Sweet' hosted significantly more beetles than the other cultivars. These two cultivars and `Legend' and `Cordele' had much more feeding damage and a significantly higher incidence of bacterial wilt than the others. A greenhouse experiment was conducted with seven of the cultivars to test their susceptibility to bacterial wilt when directly inoculated with the causal agent. All cultivars were equally susceptible to the disease when it was introduced directly into the plant. Selective feeding by striped cucumber beetles was probably most responsible for `Makdimon', `Rocky Sweet', `Legend', and `Cordele' having greater incidences of bacterial wilt than the other cultivars.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.