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 (e.g., Phytopythium vexans) has proven insufficient to reproduce KVDS symptoms, with studies suggesting root flooding as a key factor in KVDS development. To date, research has provided insights into the response of A. deliciosa to individual stress factors; however, little is known about how these plants cope with stress combinations. We characterized the transcriptome response of Actinidia deliciosa cv. Hayward over time under biotic stress (inoculation with P. vexans), abiotic stress (root flooding), and their combination, mimicking KVDS development. This study reveals that although typical flooding responses (e.g., anaerobic metabolism shift, ethylene signaling) were present under combined stress, the overall transcriptomic profile was distinct and not predictable from individual stress responses. Notably, in the presence of flooding key biotic defense mechanisms were suppressed, including phenylpropanoid biosynthesis and auxin signaling, despite their upregulation during infection with P. vexans alone. These results suggest that KVDS may involve an interaction between stressors, in which abiotic stress responses could come at the cost of plant defense mechanisms.
Guaschino et al. (Mon,) studied this question.