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How to choose among the hundreds of oil varieties?

Numbers and characteristics of a huge genetic heritage which has to be known in order to characterize and differentiate one’s own extra virgin oil

The oil is endowed with a high complexity because of it didn’t endure any genetic selection and because of olive is a long-living and resistant tree. Thanks to these characteristics up to now there are more than 1,200 different olive cultivars in the world. Among the above, 538 varieties are present in Italy, corresponding to the 42% circa of the cultivar of the world. Notwithstanding these big numbers, the world olive culture is based on some tens of varieties.

All the same, this is probably an underestimation of the total number of cultivars since there are a number of sub-varieties still not well identified.
The research in this field is complex work because the 80% circa of the olive genetic information is contaminated by the presence of viruses that induces genetic expression mutations, hence morphological changes. So, the characterization of the genetic heritage is a very complex task also by employing molecular biology techniques, such as DNA essays.

The choose among different cultivar should be based on the following parameters:

· Environmental factors. Already Caton (III-II a.C.) explained that the olive cultivar should be chosen according to the territory.

· Structural factors (Dimension, soil slope, staff availability).

· Economical factors (Investment and liquidity availability).

· Legal conditions (local laws).

So, by considering that the variety should be also chosen by considering the reference market (target), the olive farmer can choose among different levels of varieties. As a matter of fact, as it is possible for fruit farmers, also in olive culture it is possible to choose among international, national or local cultivars.

An international cultivar is a variety that is able to produce oil with similar characteristics in different regions. Nowadays, the following are considered as international: Arbequina, Koroneiki, Arbosana, Picual, Manzanilla, Barnea, Picholine, Mission, Frantoio, Coratina, Leccino, Fs 17 and Urano.

On the other hand, the national cultivar is a variety that can give a homogeneous production in different regions of a same national territory. As for Italy, are national varieties the Pendolino, the Coratino and the Moraiolo; for Spain the Picudo and the Hojiblanca; for Greece the Konservolia and the Kalamata; for Tunisia the Chemlali and for Portugal the Galega.

The new frontier in this field is the DNA extraction from oil for the variety identification. This requires the development of new techniques for DNA extraction and the identification of new molecular markers.

As a matter of fact, the kits available for the DNA extraction from the tree or from the oil show:

· Low performances

· Low DNA amplificability through Pcr

· Low reproducibility of results

Furthermore, by considering that the DNA which is present in the oil is meaningfully degradated (short-sequences only) and that it is necessary to provide for simple and variety-specific profiles, up to now the most reliable approach seems to be the employment of plastidial markers, which exclude contaminations by insect DNA.

by Alberto Grimelli
04 may 2009, Technical Area > Olive & Oil

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