Abstract
Powdery mildew, caused by Podosphaera aphanis, poses a significant threat to strawberry production, while current chemical controls raise environmental and food safety concerns. In this study, we have identified the key regulatory module, FaMYB63/FvWRKY75-PR10.14, that confers enhanced powdery mildew resistance in transgenic strawberry (Fragaria vesca). FaMYB63, an R2R3-MYB transcription factor, was induced by P. aphanis infection and responsive to the application of defence signalling molecules, including salicylic acid (SA), methyl jasmonate (JA), abscisic acid (ABA), and 1-aminocyclopropane-1-carboxylic acid (ACC). Silencing of FaMYB63 led to reduced SA levels and increased powdery mildew susceptibility, accompanied by suppressed reactive oxygen species (ROS) bursts and down-regulation of PR10.14 expression. Conversely, overexpressing PR10.14 in transgenic lines inhibited P. aphanis spore germination and enhanced ROS accumulation, indicating a dual role in direct pathogen inhibition and hypersensitive response-triggered defence. Yeast one-hybrid, electrophoretic mobility shift assay, β-glucuronidase, and luciferase assays confirmed that FaMYB63 and FvWRKY75 were directly bound to the MYB-binding sites and W-box of the PR10.14 promoter, respectively, and activated its transcription, while WRKY75 negatively regulated the expression of MYB63. PR10.14 exhibited tissue-specific expression, with the highest levels in red-ripening fruits, suggesting a role in developmental-stage-dependent defence. These findings suggest FaMYB63 as an SA-dependent regulator of PR10.14-mediated resistance, bridging hormone signalling and pathogen response. This study provides a molecular target for breeding powdery mildew-resistant strawberry cultivars through genetic engineering approaches, offering an alternative to fungicides for sustainable and environmental disease management in horticultural crops and advances our understanding of MYB- or WRKY-PR10P networks in plant immunity.