Assessing the drought response of the wild potato relative Solanum brevicaule from contrasting environments

Climate change threatens global food security, particularly for drought-sensitive crops such as potato (Solanum tuberosum). The use of crop wild relatives in breeding remains limited by scarce phenotypic and genotypic information, hindering germplasm selection and conservation planning. In this study, we evaluated the drought response of six genotypes of the wild potato Solanum brevicaule, collected from two contrasting environments within Los Cardones National Park. Plants were subjected to well-watered (WW) and water-deficit (WD) treatments under common garden conditions. Biomass partitioning, yield components, physiological and anatomical traits, and damage- and defense-related responses were evaluated. Water deficit reduced tuber number, tuber weight, stomatal conductance, and leaf relative water content across genotypes, indicating a common plastic response. However, performance and defense traits showed strong site-dependent patterns. Genotypes from the drier site exhibited higher biomass and yield under WW and maintained a stable harvest index under WD, together with increased accumulation of phenolic compounds. In contrast, genotypes from the more humid site displayed lower growth but greater plasticity in water-use efficiency (δ¹³C) and higher proline accumulation under WD. The relative contribution of site and genotype varied among traits: growth and allocation traits were influenced by both factors, whereas stomatal conductance and photosynthetic efficiency were mainly genotype-dependent, and leaf water status responded uniformly across all genotypes. These results reveal contrasting drought-response strategies in S. brevicaule. This study provides key phenotypic insights to support germplasm conservation and the use of wild relatives in breeding drought-resilient potato cultivars.