Identifying the Distribution and Causal Pathogens of Blueberry Stem Blight Disease in Alabama and Nearby States

Botryosphaeria stem blight is a fungal disease of blueberry caused by members of the Botryosphaeriaceae family that can lead to rapid wilting of leaves and stems, often resulting in significant yield loss and even plant death. Botryosphaeria stem blight is a major disease in Alabama; however, information on the distribution and causal pathogens for stem blight in Alabama is limited. This study surveyed blueberry farms in Alabama and nearby parts of Georgia and Mississippi to reveal the occurrence, species identities, and virulence of causal pathogens for Botryosphaeria stem blight. As part of this work, a total of 45 symptomatic blueberry samples were collected between 2021 and 2023. Phylogenetic analysis based on DNA sequences of the internal transcribed spacer, β-tubulin, and EF1-α genomic regions revealed that Botryosphaeriaceae (34%) was the most common family associated with disease samples, followed by Sporocadaceae (21%), Diaporthaceae (13%), Pleosporaceae (9%), and other families. Within Botryosphaeriaceae, Neofusicoccum and Lasiodiplodia were the most common genera identified. Virulence testing on the blueberry cultivar Vernon using an attached-stem assay showed that isolates of Neofusicoccum kwambonambiense, Neofusicoccum sp., Lasiodiplodia sp., N. parvum, and N. ribis caused the longest lesion length 4 weeks after inoculation compared with isolates of other genera and species. Results of this study provide the latest information on the distribution, pathogenicity, and virulence of blueberry stem blight pathogens in Alabama and nearby states. Aggressive isolates identified in this study may be useful for screening blueberry cultivars for stem blight tolerance.