Decoding Kiwifruit Vine Decline Syndrome (KVDS): from microbial ecology to molecular diagnostics and host stress responses

Kiwifruit vine decline syndrome (KVDS) poses a significant and growing threat to Actinidia deliciosa cultivation, particularly in Italy, Europe's leading kiwifruit producer. Characterized by rapid canopy collapse and root system degradation, the syndrome has an unclear etiology and severe impact on yield. This study aimed to comprehensively characterize the microbiome associated with KVDS-affected orchards in Northwestern Italy, encompassing oomycetes, fungi, and bacteria across multiple belowground compartments. It also investigated microbial dysbiosis, co-occurrence networks, and their relationships with soil physicochemical properties to better understand factors contributing to disease onset. To address diagnostic gaps, a novel molecular tool was developed and validated for the specific detection of Phytopythium vexans, accounting for host cross-reactivity and enabling quantification in roots and soil. At the host level, the study explored the transcriptomic responses of A. deliciosa to biotic, abiotic, and combined stressors, providing the first experimental insights into the plant’s molecular responses under multifactorial stress. These findings offer new perspectives on KVDS pathogenesis and highlight potential candidate genes for improving stress resilience through breeding or biotechnological approaches.