Screening frost-tolerant kale (Brassica oleracea L. var. acephala) genotypes through cold-responsive metabolic changes in open field conditions

Kale ( Brassica oleracea L. var. acephala) is a cold-tolerant leafy vegetable whose metabolic plasticity under frost stress remains underexplored. In this study, leaf tissues from 26 kale accessions grown under open-field conditions were metabolically profiled, focusing on soluble sugars, glucosinolates, and photosynthetic pigments before and after exposure to short-term frost. Frost stress induced significant quantitative and compositional shifts in sugar profiles, notably an accumulation of sucrose, suggesting its role as a key osmoprotectant. Among the twelve glucosinolates identified, indolic compounds dominated the unfrosted profile (67.4 %) but declined post-frost (51.6 %), coinciding with a marked increase in aliphatic glucosinolates (from 20.7 % to 38.6 %). Chlorophyll and carotenoid contents declined in most accessions following frost exposure. Notably, the metabolic profile of Accession_4 indicates a potentially resilient phenotype, characterised by limited pigment degradation and a shift toward aliphatic glucosinolates. This may reflect a stress-adaptation strategy and could be explored as a candidate for breeding or metabolotype selection approaches. • Kale adapts to frost through metabolic shifts, impacting its biochemical profile. • Sucrose acts as an osmoprotectant, increasing in frost-tolerant accessions. • Glucose decreases under cold stress, suggesting its role in stress responses. • Aliphatic glucosinolates increased after frost, while indolic decreased.