Thanks to the genome sequencing of 20 varieties of Sicilian oranges, mutations capable of revealing the origin, evolution and differentiation of oranges have been identified, useful for the genetic traceability of red-fleshed oranges, such as Moro and Tarocco. The study, entitled “Deep resequencing unveils novel SNVs (SNPs), Indels, and large structural variants for the clonal fingerprinting of sweet orange (Citrus sinensis (L.) Osbeck)” - (“Deep resequencing unveils novel SNVs (SNPs), Indels, and large structural variants for the clonal fingerprinting of sweet orange (Citrus sinensis (L.) Osbeck))”-, carried out by Crea Olivicoltura Frutticoltura Agrumicoltura of Acireale (Sicily), thanks to the large citrus heritage available in its collections, was published in the international journal The Plant Genome.

The analyses, carried out on 20 accessions of sweet orange, different in nutritional composition (anthocyanins and lycopene), ripening periods, fruit acidity and belonging to different varietal groups, have allowed us to identify the mutations capable of differentiating them from each other, identifying the markers that contribute to revealing their origin and diversification: data in hand, the origin of pigmented oranges could date back to a specific group of common blond oranges. The study, therefore, allows us to outline the evolution and history of pigmented oranges.

Citrus germplasm is, in fact, characterized by a wide variability, deriving from spontaneous mutations, which causes the diversification of oranges in the main varietal groups (common, Navel, Valencia, Tarocco, Sanguigno, Sanguinello, Moro), characterized by substantial differences between them. The new markers identified, moreover, represent a system for the traceability of plants and fruits of the Tarocco and Moro varieties, for which the classic molecular markers hardly work. These oranges, in fact, with the passage of time, spontaneously accumulate mutations in their DNA, thus making themselves genetically different from the samples sequenced at the beginning and from which the mutations were identified. These new markers, in addition to others that could be identified by the resequencing of other varieties of sweet orange, could contribute to the protection of agri-food products from possible fraud.

"For the first time," explains Concetta Licciardello , senior researcher at Crea Olivicoltura Frutticoltura Agrumicoltura and one of the authors of the work, "orange clones typical of local Sicilian citrus growing have been resequenced, belonging to the Moro, Tarocco and Sanguinello varietal groups, in addition to common varieties, Navel and Vaniglia, which differ from each other for a specific characteristic such as the presence of lycopene, or for the absence of acidity. Our data confirm that oranges originated only once, several thousand years ago, from the natural cross between an ancestral mandarin and a pummelo, and that only the advent of spontaneous mutations gave rise to the enormous variability that we observe today. DNA analyses have proven to be fundamental for the traceability of specific clones of Tarocco and Moro oranges: the variations in DNA available today (such as SNPs, small and large insertions and deletions, or additions and losses of portions of DNA)," he concludes, "are able to distinguish very specific orange clones, making it possible to trace both plants and juices of the same varieties".

“The study of plant genes,” comments Andrea Rocchi , president of Crea, “is increasingly a strategic asset for agricultural research. This is why I welcome with great satisfaction this latest work by Dr. Licciardello and the entire Crea team involved, which marks a further step forward in the knowledge of citrus DNA.”

Attached to this EFA News is the full text of the Crea study.