Identifying the distribution, causal pathogens, and potential solutions for managing Botryosphaeria stem blight disease of blueberry in Alabama

Abstract

In response to the surging global demand for nutritious foods, blueberry production has doubled in the last decade. However, sustainability of blueberry production is challenged by diseases such as Botryosphaeria stem blight, which is caused by fungi in the Botryosphaeriaceae family. Botryosphaeria stem blight can lead to rapid leaf wilting, chlorosis, reddening, and distinct stem discoloration, often resulting in significant yield loss. Management options are largely limited to cultural practices due to the limited success of chemical controls. Currently, no blueberry cultivar is known to have sufficient and lasting resistance to Botryosphaeria stem blight. The identification of resistant genotypes is hindered by knowledge gaps in isolates’ identity and virulence, as well as non-standardized screening protocols. To address these challenges, this study surveyed blueberry stem blight pathogens in Alabama and surrounding regions to evaluate the distribution and identity of the causal pathogens. A total of 47 symptomatic blueberry samples were collected from Alabama, Georgia, and Mississippi between 2021 and 2022. Phylogenetic analysis based on three genomic regions revealed that species in the Botryosphaeriaceae were encountered on 36% of disease samples, followed by other families such as Sporocadaceae (13%) and Diaporthaceae (11%). Within Botryosphaeriaceae, Neofusicoccum and Lasiodiplodia are the most common genera. Virulence testing using attached-stem assay showed that isolates of Neofusicoccum species caused longest lesion length four weeks after inoculation. Inoculating four blueberry cultivars ‘Star’, ‘Legacy’, ‘Miss Alice’, and ‘Vernon’ with Neofusicoccum parvum and Neofusicoccum sp. confirmed virulence of the isolates and revealed significant difference in lesion length due to treatment and cultivar, but no treatment x cultivar interaction (P < 0.05) was detected. Based on our findings, eighteen blueberry cultivars are currently being screened with the same two species. We hope to uncover sources of resistance to Botryosphaeria stem blight from this larger-scale screening and contribute to sustainable blueberry production.