LA11-88 sweetpotato breeding line exhibited enhanced drought tolerance through improved carbon partitioning and metabolic responses during early growth relative to 'Beauregard'.

Sweetpotato is widely grown across diverse agroecological areas due to its broad adaptability. However, drought stress significantly reduces productivity by causing morphological, physiological, and metabolic changes. This study examined the carbon partitioning and metabolic responses during the early growth stage of two genotypes, LA11-88 and 'Beauregard', under water deficit in a controlled growth chamber with two irrigation treatments: 100% crop evapotranspiration (ETc) as control and 50% ETc as drought stress (DS). Drought significantly reduced aboveground and belowground growth, net carbon assimilation, and stomatal conductance in both genotypes. However, differences were genotype-specific, with LA11-88 showing modifications in traits associated with drought tolerance. While 'Beauregard' favored vine elongation, LA11-88 allocated more carbon to stem diameter and total biomass. Under drought, LA11-88 displayed enhanced root architectural traits, including increased root length, volume, surface area, and diameter, supporting superior physiological tolerance and storage root development. In contrast, 'Beauregard' developed longer but thinner roots, reflected by its higher specific root length and specific root area. Drought increased sucrose and starch accumulation in leaves and storage roots of both genotypes, with a stronger increase in LA11-88. GC-MS profiling identified 31 leaf and 47 fibrous root metabolites, with higher accumulation of sugars, organic acids, and amino acids under drought, particularly in LA11-88. LA11-88 exhibited overall superior drought resilience, with a stress tolerance index of 0.61 compared to 0.31 for 'Beauregard'. A novel contribution of our study is the comparison of drought-tolerant and susceptible sweetpotato genotypes, which reveals distinct adaptation traits associated with drought tolerance and highlights LA11-88's suitability for arid environments and breeding programs.