Plant resistance to the whitefly Bemisia tabaci is compromised in salt-stressed Capsicum

Climate change has profound effects on crop production, for example through increasing temperatures, and more frequent extreme weather events. Climate change can also lead to increased pest pressure. How plants cope under double stress conditions is dependent on pest species, environment, and plant genotype, and for many plant-insect interactions, this knowledge is lacking. The whitefly Bemisia tabaci is an important pest worldwide and can be destructive for pepper (Capsicum) production. Breeding resistant varieties could aid in combatting whiteflies in a sustainable manner. In this study, we aimed to identify Capsicum accessions with resistance to B. tabaci, and study how this resistance was affected by salt stress. We grew 25 Capsicum accessions under salt treatment, and measured B. tabaci survival and oviposition. We identified four accessions with increased whitefly resistance, exhibited as higher adult mortality. Under salt stress, growth of most accessions was inhibited, and Na⁺ accumulated in shoots. Importantly, in all plants that had experienced salt stress, whitefly survival and oviposition increased, essentially nullifying resistance in salt-stressed plants. When plants were treated with salt, the phytohormone jasmonic acid was reduced compared to whitefly-infested plants without salt, possibly resulting in reduced defense to whiteflies. The results of this study will contribute to a better understanding of pest resilient plants in a changing climate.