# Identification and Characterization of Botryosphaeria dothidea Associated with Sweet Cherry (Prunus avium L.) Branch Dieback Disease in Greenhouses of Liaoning, China

## TL;DR

A study in China identifies Botryosphaeria dothidea as the cause of branch dieback disease in greenhouse-grown sweet cherries, which worsens under environmental stress and affects fruit quality and yield.

## Contribution

The study identifies Botryosphaeria dothidea as a new pathogen causing branch dieback in sweet cherries in China and explores its environmental stress-induced pathogenicity.

## Key findings

- Botryosphaeria dothidea was identified as the causal agent of branch dieback in sweet cherry cultivar ‘Tieton’ in Liaoning greenhouses.
- The pathogen can shift from an endophyte to a pathogen under environmental stress, leading to disease outbreaks.
- Optimal growth conditions for the pathogen were found to be 25–28 °C and pH 6.0–8.0.

## Abstract

China is one of the major sweet cherry-producing countries worldwide, and in particular, its greenhouse cultivation area accounts for a substantial proportion globally. Scientific management of sweet cherry diseases is a critical issue to be addressed in the greenhouse sweet cherry cultivation industry. Identifying the species and occurrence regularity of pathogenic microorganisms is the foundation of scientific disease prevention and control. The results of this study indicate that the branch dieback disease of the sweet cherry cultivar ‘Tieton’ is a fungal disease caused by the infection of Botryosphaeria dothidea. Notably, when the host plants are subjected to environmental stress, this pathogen can transform from an endophyte into a pathogenic fungus, aggravating disease occurrence and even triggering disease prevalence. This disease not only impairs the tree vigor of sweet cherries but also degrades fruit quality and reduces yield. In view of the differences in the biological adaptability of the pathogen, optimizing greenhouse cultivation conditions, rationally planting resistant cultivars, and applying chemical fungicides in a timely manner are of great significance for controlling the prevalence of this disease.

Between 2022 and 2024, a severe branch dieback disease was observed affecting over 6% of sweet cherry trees of the ‘Tieton’ cultivar in commercial greenhouses in southern Liaoning Province, China. Symptoms primarily occurred at the top of young branches. At the early stage of disease onset, the lesions appeared as dark brown, irregularly shaped areas with a moist surface; as the disease progressed, these lesions turned dry and rotten, leading to tree decline symptoms in sweet cherry trees. Disease diagnosis was carried out in sweet cherry greenhouses across Liaoning Province, where 24 diseased samples were collected and 14 fungal isolates were obtained therefrom. Based on morphological traits, cultural characteristics, and multi-locus phylogenetic analyses of the internal transcribed spacer (ITS) region, beta-tubulin (TUB2) gene, and translation elongation factor 1-α (TEF1) gene, these isolates were identified as Botryosphaeria dothidea. Two representative isolates, namely zdcy-1 and zdcy-2, were selected for pathogenicity assays. Both mycelial plug and spore suspension inoculation methods confirmed the pathogenicity of the pathogen. The biological characteristic assays revealed that the optimal temperature range for the pathogen’s mycelial growth on PDA medium was 25–28 °C, and the optimal pH range was 6.0–8.0. This study improves the understanding of branch dieback disease in sweet cherry orchards in China, enriches the knowledge regarding the geographical distribution, host range, and infection sites of the pathogen, and provides novel insights for the management of sweet cherry diseases.