Biochemical Responses of Atacama and Blesbok Sweet Potato (Ipomoea batatas L.) Cultivars to Early Drought Stress

Sweet potato is a nutrient-dense crop with the potential to improve food security, yet its productivity is constrained by drought stress. Metabolic profiling in sweet potato, particularly in response to abiotic stress, remains poorly understood, with limited knowledge on the metabolites contributing to drought response. The study aimed to profile and compare metabolites in drought-tolerant (cv Atacama) and drought-susceptible (cv Blesbok) sweet potato cultivars under water-deficient conditions. The cultivars were grown in a rainout shelter during the 2024 growing season at the Agricultural Research Council-Vegetable and Industrial Medicinal Plant (ARC-VIMP). The trial was laid out in a randomized block design with a plot size of 242 m squared with three drought treatment conditions, i.e., 30%, 50%, and 70% field capacity (FC). After two weeks of drought stress imposition, leaf samples were collected and analyzed for metabolite changes using untargeted ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). Using chemometrics analysis, mainly using principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA), significant separation was shown between the three drought stress conditions and the two cultivars, highlighting variable metabolic accumulation. Ten significantly regulated metabolites were identified (VIP > 1, p < 0.05), with the most pronounced log₂ fold changes observed for kaempferol-3-O-galactoside (3.48), chlorogenic acid (3.34), glc-glc-octadecatrienoyl-sn-glycerol (3.14), and apigenin-7-O-β-D-neohesperidoside (2.71). Metabolite concentration varied in the two cultivars, although most were positively correlated with Atacama. Enriched pathways included flavonoid biosynthesis, zeatin biosynthesis, and starch and sucrose metabolism. These findings highlight cultivar-specific metabolic responses and propose candidate biomarkers for breeding drought-tolerant sweet potato.