AIMS, METHODS, AND ADVANCES IN BREEDING OF NEW OLIVE (OLEA EUROPAEA L.) CULTIVARS

The olive industry today requires new cultivars adapted to modern intensive mechanized orchards. Narrow erect trees for mechanical harvest, adaptability to irrigation, uniform maturation, minimal alternate bearing, and resistance to leaf and root diseases are the goals of most present olive breeding programs. The development of new olive products and freezing resistance are also considered. Seedling populations of free, cross- and self-pollinated trees enabled to establish genetical dominance for the F₁ progeny. Tree clones with specific genetical characters were selected and used as gene sources for crossing on the F₁, F₂ and F₃ levels. Optimizing of the pruning, training, irrigation and nutrition hybrids, caused a marked shortening of their juvenile phase. First fruit productions in more than 50% of the seedlings was 3–4 years after seed germination. Although protoplast cultures and embryonic callus have been established, their use for breeding of olives is still limited due to insufficient morphogenesis in cultured tissues. Presently new tree clones with erect growth, high oil content, cycloconium resistance and high fruit production are being tested. Various Olea species which might introduce resistance to Verticillium wilt are presently being used in various breeding programs.

Olive culture is one of the oldest agricultural tree crops. As it was part of the traditional agriculture many local cultivars developed over the years. More than two thousand recorded cultivars, clones or subclones are still in use. Very few cultivars are grown commercially in more than one region or country. This is true particularly for the traditional olive growing countries.

The productivity of the olive tree in the traditional cultivation systems is relatively low. Long term average yields of 2.5 metric tons per hectare are considered high. On the other hand the production potential of many olive cultivars is 4–5 times higher when grown under intensive, irrigated, modern growing conditions (Hartmann, 1983; Crescimanno, 1965). However tree size and shape often changes with intensification as does also fruit development and oil accumulation (Spiegel, 1955).

For future viability of the olive as a commercial industry it is essential that production efficiency, uniformity and operation costs will be set on more economical basis (Lavee, 1983). Presently the olive industry suffers from a number of severe draw backs such as alternative bearing, low fruiting ability, expensive manual harvest, lack of varietal standardization, etc. Tree form, fruiting habits, fruit quality, production efficiency and resistance to diseases and