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Botryosphaeriaceae associated with stem blight and dieback of blueberry (Vaccinium corymbosum) in Australia

Rosalie Daniel: NSW Department of Primary Industries

<div>Stem blight and dieback due to Botryosphaeriales fungi have become more prevalent on blueberry in Australia. A small-scale survey was undertaken to determine the species associated with the disease and to gather information on possible causal agents. Fifty-two isolates were collected from two orchards in the main blueberry growing areas in New South Wales and four isolates from a single orchard in Western Australia. A multi-locus sequencing approach was used with the internal transcribed spacer region of rDNA including 5.8S (ITS), partial translation elongation factor 1-alpha (tef1-α), and DNA-directed RNA polymerase II second largest subunit (rpb2). Eight species from three genera of the Botryosphaeriales were identified; the most common was <em>Neofusicoccum parvum</em> (n=34), followed by <em>N. kwambonambiense</em> (n=7), <em>N. occulatum</em> (n=5), <em>Lasiodiplodia theobromae</em> (n=2), <em>Botryosphaeria dothidea</em> (n=1), <em>N. australe</em> (n=1), <em>N. macroclavatum</em> (n=1) and <em>L. pseudotheobromae</em> (n=1). A detached stem assay used to evaluate pathogenicity showed that all isolates were able to initiate lesions on twigs of blueberry cultivar C99-42. Botryosphaeriales isolated from blueberry have also been reported in other horticultural crops and in native Australian woody plants. Blueberry orchards often occur near natural vegetation or other crops. Cross-infectivity has been demonstrated for some species. Diseases caused by wood-infecting pathogens are a major impediment to blueberry production. This study provides the first survey of Botryosphaeriales associated with blueberry stem blight and dieback in Australia, and is a valuable resource for plant pathologists and growers trying to manage the disease.</div>