A novel approach for propagation of recalcitrant pistachio cultivars that sidesteps rooting by ex vitro grafting of tissue cultured shoot tips

Pistachio (Pistacia vera L.) cultivars need to be grafted on suitable rootstocks for their propagation, but grafting success is uncertain, preventing producers to meet plant demand. Thus, there is a need for a better grafting method that in addition to increase success rate, allows us an early detection of success. Here, we have developed an alternative grafting technique that achieves these goals using young potted seedlings of terebinth rootstock and reduced size micropropagated scions from commercial cultivars. During micropropagation of pistachio cultivars we studied the effects of the application of antioxidants together with the growth regulators meta-topolin and paclobutrazol on in vitro cultures to overcome the issues identified in the different phases of micropropagation: culture initiation, multiplication and rooting. Grafting succeeded using scions derived from in vitro cultured micro-shoots both from acclimated and non-acclimated plants. With this protocol, up to 75.7 % successful grafts were obtained, and grafted plants resumed growth from day 3, being ready for transplant a few months later. Sustained on our results, we present a simple and reliable system to reduce production time by ex-vitro grafting of shoot-tips from in vitro cultures onto 4 weeks old terebinth (Pistacia terebinthus L.) rootstock seedlings grown in pots.