Metabolic alterations in moderately resistant West Coast Tall and susceptible Chowghat Orange Dwarf coconut varieties in response to exotic whitefly infestation

Abstract

In a metabolomics analysis using GC–MS, we explored the metabolic responses of moderately resistant West Coast Tall (WCT) and susceptible Chowghat Orange Dwarf (COD) coconut varieties to infestation by the exotic whiteflies Aleurodicus rugioperculatus and Paraleyrodes bondari. WCT exhibited a low to medium Infestation Grade Index (IGI) for both whitefly species, while COD displayed a medium to high IGI. Additionally, the study examined the preferential feeding behavior of the whiteflies, highlighting their tendency to predominantly infest the bottom leaves rather than the top leaves. GC–MS analysis of healthy top leaves and whitefly-infested bottom leaves from the WCT and COD coconut varieties identified 56 metabolites, categorized into carbohydrates, fatty acids, organic acids, amino acids, and secondary metabolites. The WCT coconut variety exhibited moderate resistance to exotic whitefly infestation through the accumulation of boric acid. Furthermore, the activation of the biosynthetic pathway for unsaturated fatty acids, leading to increased levels of docosahexaenoic acid and arachidonic acid, played a significant role in its defense response. In WCT, the uninfested top leaves showed higher levels of shikimic acid, stearic acid, threonic acid, lactic acid, and palmitic acid, suggesting these compounds contribute to its defensive strategy. The abundance of sugars in the bottom leaves of COD likely facilitated the feeding and development of the whiteflies, making it a more favorable host for the pest. This study highlights distinct metabolic responses to whitefly resistance and lays the foundation for future research aimed at developing pest-resistant coconut cultivars.