Characterization of Botrytis fabiopsis and B. euroamericana associated with blueberry (Vaccinium corymbosum) blossom blight in Michigan

Botrytis blossom blight and fruit rot are important diseases of blueberry in Michigan, traditionally attributed to Botrytis cinerea. However, a recent survey revealed the presence of additional Botrytis species associated with these diseases. During the survey, three isolates from Botrytis populations collected from blueberry fields were genetically examined and identified as B. fabiopsis and B. euroamericana based on multilocus phylogenetic analysis, prompting the need for further characterization of these emerging pathogens. This study aimed to characterize these isolates through expanded multilocus phylogenetic analysis incorporating five gene regions (G3PDH, RPB2, HSP60, NEP1, and NEP2), as well as assessments of their morphological traits, growth behavior, pathogenicity, and fungicide sensitivity. These isolates exhibited optimal growth temperatures between 20 - 25 °C and demonstrated cultural traits consistent with their respective species. Pathogenicity tests confirmed their ability to infect healthy blueberry flowers and leaves, along with white rose petals and table grapes. Fungicide sensitivity profiling revealed that all isolates were sensitive to seven commonly used fungicides, although two showed reduced sensitivity to cyprodinil. This study provides the first experimental evidence confirming the pathogenicity of B. fabiopsis and B. euroamericana on blueberry tissues in Michigan and contributes key insights into their biological behavior and management potential.