Integrated physiological, biochemical and hormonal traits determine drought tolerance and yield stability in cashew (Anacardium occidentale L.)

Drought stress, intensified by climate change, represents a major limiting factor to growth, reproductive development, and nut productivity of cashew (Anacardium occidentale L.), especially in rainfed and marginal production systems. Identifying drought-tolerant cultivars and understanding their adaptive mechanisms are therefore critical for sustaining cashew productivity in water-limited environments. In this study, seventeen cashew varieties were evaluated under drought stress to identify tolerant genotypes and elucidate the physiological, biochemical, metabolic, and hormonal mechanisms underlying drought adaptation. A multi-trait genotype ideotype distance index (MGIDI) was employed to integrate diverse traits for robust genotype ranking and holistic drought tolerance assessment. The analysis identified ‘Priyanka’ and ‘Bhaskara’ as drought-tolerant varieties, whereas ‘Ullal-2’, ‘Vengurla-2’, and ‘Madakkathara-1’ were classified as drought-sensitive. Drought stress resulted in a significant reduction in nut yield (63.2%), accompanied by impaired nutrient uptake, reduced chlorophyll content (59.7%), and compromised membrane integrity, with more pronounced effects in sensitive varieties. In contrast, tolerant varieties showed increased antioxidant enzyme activities, including ascorbate peroxidase and polyphenol oxidase, along with increased accumulation of stress-responsive metabolites such as proline and soluble sugars, which contributed to improved oxidative stress mitigation and osmotic adjustment. Drought tolerance was further linked to differential accumulation of phenolic acids and flavonoids as well as higher endogenous levels of abscisic acid, jasmonic acid, and indole-3-acetic acid, all of which were positively correlated with nut yield under drought conditions. This integrated MGIDI-based assessment links coordinated physiological, metabolic, and phytohormonal responses to drought tolerance in cashew, offering robust selection criteria for breeding and deploying climate-resilient cultivars in drought-prone areas.