A multidisciplinary, cross-species approach to understanding woody plant declines: similarities between Kiwifruit Vine Decline Syndrome (KVDS) and Apple Replant Disease (ARD)

Kiwifruit Vine Decline Syndrome (KVDS) and Apple Replant Disease (ARD) are both soil-borne diseases affecting fruit trees in perennial cropping systems. Both pathosystems are characterized by a similar complex of soilborne fungi and oomycetes which impact root development and soil health. ARD occurs in apple-producing regions worldwide. In the last decade, KVDS has severely compromised kiwifruit production in Italy and has also been reported in Turkey, Japan, and China. The contribution of similar biotic and abiotic factors to both pathosystems underlines the need for multidisciplinary and cross-species approaches to the management of woody plant diseases. This is of particular relevance in the framework of climate change where novel conditions may lead to shifts in microbial community composition and function. Root anoxia/flooding of the radical system is a key abiotic stress factor required for development of KVDS symptoms, together with infection by Phytopythium vexans. Preliminary gene expression analysis on kiwifruit roots revealed upregulation of ROS scavenging pathways and hormonal stress at specific time points in response to this dual stressor combination. Additional transcriptomic studies on inoculated Actinidia roots, with and without flooding, are currently underway. Results are expected to improve our understanding of how pathways associated with abiotic vs. biotic stress factors promote KVDS onset. In combination with this analysis, genes previously identified as exhibiting altered expression in apple roots in response to Pythium ultimum infection will serve as a foundation to explore potential similarities in KVDS and ARD pathosystems. Results are expected to provide new insights into oomycete pathogenesis in woody plants and improve disease management in both systems.