Identification and pathogenicity of Botryosphaeria species associated with grapevine decline in Western Australia

Botryosphaeria species have recently gained importance as pathogens of grapevines worldwide. A survey was conducted of 16 vineyards in three grape-growing regions in Western Australia to determine if Botryosphaeria species were playing a role in grapevine decline. B. australis, B. rhodina, B. obtusa and B. stevensii were isolated from grapevines exhibiting symptoms of decline, and identified based on morphological characteristics and ITS sequence data. These species have all been isolated from grapevines elsewhere in the world. Regional differences between Botryosphaeria species were apparent. B. rhodina was isolated only from the Swan Districts region. B. australis was present in the Margaret River and Pemberton/Manjimup regions, but was never isolated from the Swan Districts region. B. obtusa was isolated from all regions, but most prominently from Manjimup, and B. stevensii was isolated only once from Manjimup. A pathogenicity trial found B. australis, B. rhodina and B. stevensii to be pathogenic to grapevines, whereas B. obtusa did not produce any lesions on the cuttings. In Western Australia, B. australis appears to be the predominant pathogenic Botryosphaeria sp. The role of other species of Botryosphaeria and the interaction between species requires further study.