Fad7 gene identification and fatty acids phenotypic variation in an olive collection by EcoTILLING and sequencing approaches

•Identification of the olive full-length fad7 gene coding the chloroplast type desaturase.•Detection of a high level of heterozygousity (1/110 bp) in this gene by sequencing.•EcoTILLING versus direct sequencing to screen the olive natural allelic variation.•Confirmation of a high level of conservation of the gene in Italian germplasm.•Evaluation of genotypic effect on overall fatty acid profile.

The ω-3 fatty acid desaturases (FADs) are enzymes responsible for catalyzing the conversion of linoleic acid to α-linolenic acid localized in the plastid or in the endoplasmic reticulum. In this research we report the genotypic and phenotypic variation of Italian Olea europaea L. germoplasm for the fatty acid composition. The phenotypic oil characterization was followed by the molecular analysis of the plastidial-type ω-3 FAD gene (fad7) (EC 1.14.19), whose full-length sequence has been here identified in cultivar Leccino. The gene consisted of 2635 bp with 8 exons and 5′- and 3′-UTRs of 336 and 282 bp respectively, and showed a high level of heterozygousity (1/110 bp). The natural allelic variation was investigated both by a LiCOR EcoTILLING assay and the PCR product direct sequencing. Only three haplotypes were identified among the 96 analysed cultivars, highlighting the strong degree of conservation of this gene.