Botryosphaeriales associated with stem blight and dieback of blueberry (Vaccinium spp.) in New South Wales and Western Australia

Stem blight and dieback caused by species of the Botryosphaeriales are important diseases of blueberry worldwide. In recent years, stem blight and dieback symptoms have been increasingly observed affecting blueberry production in Australia. Thirty samples were collected from symptomatic plants in an orchard at Corindi NSW, a major blueberry growing region. In addition, samples from symptomatic blueberry plants were submitted by growers to the Plant Health Diagnostic Service, NSW Department of Primary Industries from eight orchards in New South Wales (NSW), and a single orchard in Western Australia (WA). Culture isolations, DNA sequencing and pathogenicity testing were undertaken to determine the species causing the disease. Fifty-two isolates were recovered in total, forty-eight from NSW, and four from WA. A multi-locus sequencing approach was used to assist species identification including the internal transcribed spacer region of rDNA including 5.8S (ITS), partial translation elongation factor 1-alpha (tef1-), and DNA-directed RNA polymerase II second largest subunit (rpb2). Eight species from three genera were identified; the most common was Neofusicoccum parvum (n=34), followed by N. kwambonambiense (n=7), N. occulatum (n=5), L. theobromae (n=2), Botryosphaeria dothidea (n=1), N. australe (n=1), N. macroclavatum (n=1) and Lasiodiplodia pseudotheobromae (n=1). The pathogenicity testing showed all isolates produced lesions on blueberry stems. This study provides the first survey of Botryosphaeriales causing blueberry stem blight and dieback in Australia, and is a valuable resource for plant pathologists and growers trying to manage the disease.