An efficient method for callus induction and shoot regeneration of Olea europea L. cv. koroneiki

Olea europea L. cv. koroneiki is a multipurpose tree which belongs to family Oleaceae . Koroneiki is famous for its virgin oil production and suitable for high density growing system around the world. Being grafted and recalcitrant in nature, Koroneiki demands an efficient in vitro protocol for its propagation and conservation. The aim of the present study was to set up an efficient protocol for in vitro regeneration of this beneficial olive cultivar. Three different basal media, Murashige and Skoog (MS), Olive Medium (OM) and Woody Plant Medium (WPM) were tested for two types of explants, leaf and nodal segments for callus induction and shoot regeneration. To find out the best explant disinfestation method during this study, explants were soaked in detergent for 15 minutes with continuous agitation. After washing, explants were rinsed with 70% ethanol for 10 seconds and finally treated with 0.1% mercuric chloride for 3 minutes and rinsed 4-5 times with autoclaved distilled water under the laminar air flow cabinet considered as most suitable for cv. Koroneiki. Media were either used alone or supplemented with 6-benzylaminopurine (BAP) (8.8 and 17.7 µM) and zeatin (4.56 and 9.12 µM) to find out suitable PGR for callus induction and shoot proliferation. Maximum callus induction (70 %) on nodal explants was observed on OM medium containing 9.12 µM zeatin+ 17.7 µM BAP under both dark and light conditions. The WPM containing the combination of BAP and zeatin showed 67% callus induction under light by using nodal explants. However, in case of leaf explants, 50% callus induction response was observed under dark conditions, but no callus was observed under light. The OM supplemented with combination of BAP (17.7 µM) and zeatin (9.12 µM) induced highest shoot length (1.5) and maximum number of leaves (3.5). This study might helpful for commercial propagation of cv. Koroneiki at mass scale under in vitro conditions to fulfill the virgin oil demand for rapidly growing population.