The improvement of olive trees

The research team, headed by Dr. Giyora Ben-Ari is part of the department of fruit trees of the institute of plant sciences at the Volcani Center.
The motto accompanying this team’s work is searching for real problems, e.g., which may have an impact on olive-tree growing in Israel today, and to offer practical solutions for these problems.
The total extent of olive-tree plantations in Israel today is estimated to be close to 300,000 dunams, 250,000 of which are grown without irrigation (dry farming), most of them in the Galilee. Of the rest 80,000 dunams under irrigation, 65,000 are olive plantations grown for the oil production industry and about 15,000 as edible olives.

Two main problems characterize olive-tree cultivation in Israel today:
1) Olive-tree oil prices;
2) Harvesting of edible olives, basically a labor-intensive practice.

 

 

One of the research’s challenges ensuing is developing means of mechanical harvesting of olive trees.
Dr. Ben-Ari, together with his research team, runs an improvement program aimed at finding and developing new olive cultivars housing specific genetic traits. Among these are high resistances to diseases, low fruit production fluctuation, greater suitability for mechanical harvesting and suitability for a super-intensive growth regime.

To attain the above-mentioned goals, an experimental plot, the size of which is 80 dunams, was established on the Center’s grounds. In this plot 150 olive cultivars which were collected from different countries around the world, are grown. These cultivars are used as a genetic reservoir, or germplasm, for the improvement program. The progeny of this program, namely, those seedlings which have passed all the selection steps, are then planted at the very same experimental plot.

 

 

 

Ben-Ari’s research group utilizes two methods in aiming at reaching its goals:
1) The conventional method, namely, crossings. Each year crossings between ten different species are carried out and 1000 fruits from these crossings are collected. The actual crossings are thus performed: the tree’s inflorescence, which contains closed flowers, is caged inside a paper bag. The following step includes the introduction into the paper bag of an inflorescence from a different cultivar which is used as the pollinator. This is done in order to bring about intentional cross pollination. In addition to collecting the fruits from the aforementioned cross pollination, another 1000 fruits, the result of a free pollination, are also collected. This method is carried out at the experimental plot where the varieties collection is found.

The progeny of the above-mentioned crosses is checked at the first stage, for two main traits: fruit size and oil content (%). This, along a growth period of five fruit-bearing (or, productive) years. At the end of this growth period, the progeny which have passed a threshold value in accordance with the two aforementioned traits, are rooted and then planted in the experimental plot. This, with the aim of selecting outstanding lines.

These are then vegetatively reproduced in three copies, planted in the experimental plot for further five fruit-bearing years and examined for a large variety of traits.  The progeny which have successfully passed the above-mentioned steps are then planted in half-commercial plots in three different geographical areas, where they will be further tested for their accordance to the commercial market’s demands. These successful cultivars are then registered as commercial varieties and are offered to growers for cultivation under commercial conditions.

 

 

The above-mentioned improvement procedure, based on the conventional method can last around thirty years. In order to circumvent this obstacle, a use is made today of genetic markers – e.g., DNA markers – in order to identify the crosses’ progeny in advance. In using this method, it will be possible in the future to characterize different traits resulting from the crosses, e.g., resistances to diseases, fruit size, and oil content (%). In addition, it will be made possible to identify the pollinator (the contributor of the pollen, which are the male fertilization organs).

 

2) Another method used by Dr. Ben-Ari and his team in order to produce new types of olive trees is irradiation of existing seedlings by gama particles. This, in order to produce mutations in these varieties.
The utilization of molecular tools makes possible the characterization of olive-tree varieties to the point of attaching to them a ‘personal identity card’ for each of them.

The olive-tree improvement program, run in Dr. Giyora Ben-Ari’s laboratory at the Volcani Center, which was described in this short article is continuing these days in utilizing both traditional (or, conventional) selection and improvement methods and using advanced, state-of-the art molecular biology methods, in order to develop new and outstanding olive tree varieties in a relatively short time and for the benefit of israel and world olive-tree growers.

 

For more info, please contact Dr.Ben – Ari at : giora@agri.gov.il