In the last decade significant progress has been made in developing successful olive cloning techniques, although some difficulties still remain such as that with establishing sterile cultures in vitro and morphogenesis from mature tissue of cultivars. More work is required, although significant advances have also been made in shoot regeneration from petioles of in vitro grown shoots of several cultivars (Mencuccini and Rugini, 1993). However, the regeneration ability is still low for use in biotechnological applications. The novel strategy of the «double regeneration», developed to achieve somatic embryos in olive cv. Canino and Moraiolo may also be applicable in other cultivars. This technique can be generalised since at present it is essential for inducing and maintaining shoot morphogenic callus in other species such as cherry, apple, and pear (Gutiérrez Pesce et al., 1998; Rugini e Muganu 1998; Abdollahi et al., 2005).
Gene transfer techniques offer a more powerful strategy for genetic improvement in respect to traditional breeding methods. It allows the introduction into one genotype, one or a few pieces of genetic information without drastic modifications of the general characteristics of the plant. Transformation techniques have been developed, by using somatic embryogenesis, and transgenic plants, with some desirable agronomic traits, have already been generated in one cultivar. At present field trials, approved by the Italian Health Minister, are conducted on transgenic rolABC, and osmotin plants.
From transgenic olive plants, similar to kiwi transgenic plants with rolABC genes we expect plants with large root systems, compact vegetative habitus, smaller number of flowers per plant, and high rooting ability of cuttings. In plants over-expressing osmotin gene, we expect a higher tolerance to some fungi. Many genes have already been isolated from several species, which may be introduced in olive singly or associated with others. Transformation experiments with multiple genes (chitinase + osmotin + PR1) are in progress in our laboratory in order to increase fungal resistance.
Antibacterial genes (thionin, cecropin, attacin, etc.) against Pseudomonas syringae and genes for modifying the pattern of fruit ripening (ethylene, PG) are only a few examples of the potential of genetic manipulation to improve olive. A high content of di-hydroxiphenols could confer the valuable bitter taste in the olive oil.
Agrobacterium-mediated gene transfer seems to be the most efficient method in olive.
The molecular techniques should not aim only to make clear the phylogenesis of the genus, but also to clone useful genes and promoters in olive. To facilitate this work, biotechnology, long-term breeding programs and biochemical research should be closely linked to achieve the objectives quickly.U zadnjem desetljeću učinjen je znatan napredak u razvijanju uspješnih metoda kloniranja maslina iako će neke poteškoće ostati, kao utvrđivanje sterilnih kultura in vitro i morfogeneza iz zrelog tkiva kultivara. Potrebno je još raditi, makar je učinjen znatan napredak i u regeneraciji izbojaka iz petiola uzgojenih in vitro od nekoliko kultivara (Mencuccini i Rugini, 1993). Međutim, mogućnost regeneracije još je uvijek mala za biotehnološku primjenu. Nova strategija "dvostruke regeneracije", razvijena kako bi se dobili somatski embriji masline cv. Ganino i Moraiolo mogu se primijeniti i u drugim kultivarima. Ova se tehnika može generalizirati jer je danas bitna za induciranje i održavanje morfogenskog kalusa izbojka u drugim vrstama kao što su trešnja, jabuka i kruška (Gutierrez Pesce et al. 1998; Rugini e Muganu, 1998; Abdollahi et al., 2005).
Tehnike transfera gena pružaju snažniju strategiju za genetsko oplemenjivanje u odnosu na tradicionalne uzgojne metode. One omogućuju uvođenje u jedan genotip jedne ili više genetskih informacija bez drastičnih modifikacija općih značajki biljke. Razvijene su tehnike transformacije primjenom somatske embriogeneze i transgenske biljke određenih poželjnih agronomskih svojstava i već su proizvedene u jednom kultivaru. Upravo se provode pokusi na terenu, koje je odobrio talijanski Ministar zdravstva, na transgenskim rolABC i osmotinskim biljkama.
Od transgenskih biljaka masline, slično transgenskim biljkama kivija s genima rolABC, očekujemo biljke velikog sustava korijena, zbijenog vegetativnog habitusa, manjeg broja cvjetova po biljci i velike sposobnosti sadnica za ukorijenjenjem. U biljaka preizraženog osmotinskog gena očekujemo veću tolerantnost na neke gljive/gljivice. Izolirani su već mnogi geni iz nekoliko vrsta, što se mogu introducirati pojedinačno ili zajedno s drugima. Pokusi transformacije s mnogostrukim genima (chitinase + osmotin + PRL) su u tijeku u našem laboratoriju, kako bi se povećala otpornost na gljivice.
Antibakterijski geni (tionin, cecropin, atacin itd.) protiv Pseudomonas syringae i geni za modificiranje uzorka zriobe voća (etilen, PG) samo su neki primjeri potencijala genetske manipulacije za oplemenjivanje masline. Visok sadržaj dihidroksifenola mogao bi prenijeti dragocjen gorki okus maslinovog ulja. Prijenos gena posredstvom agro-bakterija čini se najdjelotvornijom metodom u masline.
Cilj molekularnih tehnika ne bi trebao biti samo razjašnjenje filogeneze gena nego i kloniranje korisnih gena i stimulatora u maslini. Da bi se taj posao olakšao potrebno je usko povezati biotehnologiju, dugoročne uzgojne programe i biokemijska istraživanja radi brzog postizanja ciljeva
