Biometric, Physiological, Biochemical and Molecular Responses of Grapevine to Flavescence Dorée Phytoplasma Infection: A Comprehensive Meta-Analysis

Flavescence dorée (FD) is a devastating quarantine disease associated with flavescence dorée phytoplasma (FDp), leading to substantial economic losses in European viticulture. Despite extensive research, the high variability in experimental results has hindered a comprehensive understanding of the grapevine’s (Vitis vinifera L.) physiological and molecular responses to infection. This study provides a large-scale synthesis of 20 peer-reviewed research papers, comprising a total of 779 observations, using a three-level random-effects meta-analysis model. This advanced statistical approach accounts for dependencies between effect sizes, quantifying the overall impact of FDp on plant productivity, metabolism, and gene expression. FDp infection significantly impairs grapevine reproductive capacity, evidenced by a 22% reduction in the fertility index. Photosynthetic machinery was severely compromised, showing an 81% decrease in chlorophyll a content and a dramatic downregulation of the Rubisco activase gene (-90%). While core energy metabolism genes remained stable, leaf primary metabolism related compounds showed significant accumulation of sucrose (+35%) and ascorbate (+42%). A key finding was the strong activation of systemic acquired resistance-related pathways, with salicylic acid levels increased by 451%. This defence response was corroborated at the molecular level by the strong upregulation of stress-related genes, such as osmotin (+829%) and thaumatin (+561%). Our meta-analysis reveals a sophisticated pathogen strategy that selectively suppresses the host’s photosynthetic and reproductive vigour while maintaining basic metabolic stability to ensure a chronic interaction. These quantitative insights provide crucial targets for resistance breeding and the development of resilience-improving management strategies in the face of ongoing FDp outbreaks.