Micropropagation and in vitro grafting techniques to assist the selection of a pistachio rootstock from a population of terebinth (Pistacia terebinthus L.) collected in the SE of Spain

Abstract

Pistachio culture is hampered both by the difficulty of propagation by grafting cultivars of interest and by the lack of a clonal selected rootstock. The application of in vitro culture techniques would allow the clonal propagation of Pistacia species, as well as to perform in-depth studies of factors affecting grafting. In vitro P. vera cultures were initiated from nodal explants, whereas cultures of P. terebinthus were initiated from in vitro-germinated seeds. The multiplication rate of both species in vitro was close to 2 shoots per shoot every 3 weeks. A high rooting percentage (82%) of P. terebinthus was obtained in a modified WPM medium and plants were successfully transplanted to the greenhouse. Shoot apices of P. vera of 10-20 mm length were grafted in vitro on rooted or unrooted shoots of P. terebinthus in which the apex was removed, and the evolution of the graft unions was studied. Over 70% of the grafted plants survived during the first 3-5 weeks and some plants continued their growth in the greenhouse. Similarly, control self-grafted P. terebinthus were studied, and these homographts showed that, while the technique of grafting in vitro is promising in studying graft evolution, it needs to be improved by identifying the factors that affect cell necrosis.