The present invention relates to a mutated nucleic acid sequence of a delta-12 oleate desaturase enzyme (FAD2)--encoding nucleic acid from a Cruciferae plant, wherein said mutated nucleic acid sequence comprises the non-conservative mutation of at least one nucleotide of at least one codon representing an amino acid selected from the group consisting of: --the amino acid at position 259 of the amino acid sequence of said FAD2, --the amino acid at position 216 of the amino acid sequence of said FAD2, --the amino acid at position 90 of the amino acid sequence of said FAD2, --the amino acid at position 116 of the amino acid sequence of said FAD2, --the amino acid at position 276 of the amino acid sequence of said FAD2.