Novel methods in micropropagation of pistachio

Abstract

The focus of this paper is to describe the novel methods developed for the different stages of micropropagation: installation of mature apical shoot tips and elimination of browning exudates; forcing hardwood shoots from the lignified stem sections; forcing axenic leaves; initiation of embryogenic masses (EMS); encapsulation of somatic embryos and cryopreservation of axillary buds for storage, and the facilitation of rooting. These developed methods are not being used by commercial micropropagation laboratories yet. Exudation of phenolics is inhibited when the disinfested and rinsed explants are cut at the base of the shoot tips and washed twice for 1 h by shaking them in sterile distilled water on a shaker at 100 rpm. For shoot initiation, 15-20 cm long terminal stem sections are cut into 3-4 cm sections and placed in pots filled with peat, perlite and soil. Two or three weeks later, the developed softwood shoots are excised; or freshly harvested three to nine apical tips of 1-2 cm are disinfested and used as explants. Leaves excised from axenic shoot cultures were also used to induce organogenesis on a Murashige and Skoog (MS) medium with Gamborg vitamins supplemented with combinations of different concentrations of 6-benzylaminopurine (BA) and indole-3-asetic acid (IAA). Calcium alginate gel was used to encapsulate somatic embryos to produce synthetic seeds. The encapsulated somatic embryos can be stored under refrigerated conditions for short-term conservation. For long-term conservation, some axillary buds can also be stored by using vitrification and one-step freezing technique; however, other cryogenic techniques should also be tested. With these improved stages, application of Pistachio vera L. micropropagation in commercial clonal orchards will be feasible as an alternative to traditional propagation in the near future. © 2017 Elsevier B.V., All rights reserved.