A new sunflower high oleic mutation confers stable oil grain fatty acid composition across environments

•Genotypes producing oils with oleic acid >90% in any environment are demanded.•The sunflower isogenic lines were non-mutated (traditional) or mutated (Pervenets and NM1).•Plants were exposed to minimum night temperatures from 11.8 to 23.2°C.•NM1 showed oleic acid percentages >91.3 and more stable concentrations than Pervenets.•Ultra-high oleic quality was obtained in NM1 independently of growing temperature conditions.