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.