EVALUATION OF THE EFFECT OF PHOSPHINOTHRICIN, AS SELECTION AGENT, ON THE GROWTH OF OLIVE SOMATIC EMBRYOS

The olive tree (Olea europaea L.) is one of the most important fruit crops in the Mediterranean area. Genetic transformation is a tool of great interest because it allows the introduction of selected traits in elite genotypes in a short time. An efficient Agrobacterium-mediated transformation system using olive somatic embryos as explants and paromomycin as selective agent has been recently developed in our lab. Using this protocol, several transgenic lines carrying antifungal genes have been obtained. A strategy to enhance fungal resistance in olive plants consists in the stacking of resistance genes in a single transgenic line. This approach requires the development of other selection strategies, alternative to the paromomycin selection. In this study, the establishment of a selection system with the herbicide phosphinothricin (PPT) using somatic embryos obtained from a seed of ‘Picual’ was attempted. The results obtained showed a significant effect of PPT at concentrations of 2.5-10 mg L^-1 in the inhibition of callus proliferation. Selection in liquid medium supplemented with PPT was more effective than in solid medium; moreover, the inclusion of a selection phase in liquid medium during three weeks in the presence of different concentrations of PPT improves the efficiency of selection with the herbicide. However, the highest PPT concentration tested, 10 mg L^-1, was not sufficient to completely inhibit the growth of the embryogenic callus.