Exploring the root response to multiple stressors: mechanisms underlying Kiwifruit Vine Decline Syndrome (KVDS) development

Authors: GUASCHINO, MICOL - University Of Torino; Somera, Tracey; Hargarten, Heidi; Honaas, Loren; ZHANG, HUITING - Washington State University; COOK, CHRIS - Washington State University Extension Service; SPADARO, DAVIDE - University Of Torino

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: First reported in Italy in 2012, Kiwifruit Vine Decline Syndrome (KVDS) has emerged as a major threat to Actinidia deliciosa (kiwifruit) vines in the Mediterranean region, significantly impacting production. Infection with biotic agents alone (e.g., Phytopythium vexans) has proven insufficient to reproduce KVDS symptoms; however, multiple studies have suggested that root flooding plays a key role in KVDS development. To date, the response of A. deliciosa to individual stress factors (including flooding) has been studied; however, little is known about how kiwi plants cope with stress combinations. Here, we characterize the transcriptomic response of A. deliciosa (Hayward) to a combination of biotic stress (inoculation with P. vexans) and abiotic stress (root flooding), reproducing KVDS symptoms under controlled conditions. This study represents the first investigation of multifactorial stress interactions in Actinidia, providing new insight into how the combined effects of biotic and abiotic stressors (P.vexans + waterlogging) lead to KVDS development. The study revealed that the transcriptomic response to multifactorial stress was unique and could not be predicted from the transcriptomic response of roots to each of the different stressors alone. The effect of flooding was dominant to the effect of pathogen infection and the ability of A. deliciosa to mount an effective defense response (especially in terms of chemical defenses) was greatly reduced in the presence of flooding. Consequently, even though the stressors applied individually to the plant have a negligible effect on plant growth/survival, the antagonistic effects between pathogen and flooding stress responses likely has a synergistic effect, leading to significant negative effects on plant growth and survival (i.e., the development of KVDS).

Technical Abstract: First reported in Italy in 2012, Kiwifruit Vine Decline Syndrome (KVDS) has emerged as a major threat to Actinidia deliciosa vines in the Mediterranean region, significantly impacting kiwifruit production. Infection with biotic agents alone have proven insufficient to reproduce KVDS symptoms; however, multiple studies have suggested that root flooding plays a key role in KVDS development. Previous studies have provided insight into the response of A. deliciosa to individual stress factors (including flooding); however, little is known about how these plants cope with stress combinations. To study the impact of a multifactorial stress combination on kiwi plants, we characterized the transcriptomic response of Actinidia deliciosa cv. Hayward over time under biotic stress (inoculation with P. vexans), abiotic stress (root flooding), and their combination, mimicking KVDS symptoms under controlled conditions. To our knowledge, this is the first investigation of biotic-abiotic interactions in Actinidia. The study revealed that the activation of multi-phytohormone signaling cascades and key enzymes (chalcone synthase) involved in phenylpropanoid biosynthesis play a major role in regulating root defense responses to the soilborne oomycete pathogen Phytopythium vexans during infection. When biotic and abiotic stressors were combined, however, the effect of flooding was dominant to the effect of pathogen infection and the ability of A. deliciosa to mount an effective defense response (esp. chemical defenses) was greatly reduced. Consequently, even though the individual stressors have a negligible effect on plant growth/survival, the antagonistic effects between pathogen and flooding likely have a synergistic effect, leading to the development of KVDS.