Identification and distribution of Botryosphaeriaceae species associated with blueberry stem blight in China

Blueberry (Vaccinium corymbosum) has developed rapidly in China over the past 20 years because of its perceived health and nutritional benefits. Blueberry stem blight, caused by fungi in the family Botryosphaeriaceae, is the most destructive disease affecting blueberry production and quality worldwide. A field survey of 20 blueberry plantations in eight provinces across China was conducted to determine the occurrence and distribution of Botryosphaeriaceae species. In total, 69 Botryosphaeriaceae isolates associated with blueberry twig dieback and stem blight were identified based on morphological characteristics and analyses of nucleotide sequences of three genomic regions: the internal transcribed spacer region (ITS1-5.8S-ITS2), a partial sequence of the beta-tubulin gene, and part of the translation elongation factor 1-alpha gene (EF1-alpha). Three species were identified, including: Botryosphaeria dothidea, Neofusicoccum parvum and Lasiodiplodia theobromae. Botryosphaeria dothidea and N. parvum were the most prevalent species and were widely distributed in all blueberry-growing regions. In contrast, L. theobromae was only found in southeastern regions. Koch's postulates showed all three species to be pathogenic when inoculated with mycelial plugs on detached and intact blueberry stems (cv. Bluecrop). Pathogenicity tests showed N. parvum and L. theobromae to be more virulent than B. dothidea. To our knowledge, this study is the first comprehensive description for morphology, phylogenetic analysis, and distribution of Botryosphaeriaceae spp. as causal agents of blueberry stem blight in China.