In vitro establishment of Olea europaea cv. Koroneiki using melatonin as a plant growth regulator

Olea europaea 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. 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. Explants 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 were considered as most suitable for cv. Koroneiki. Maximum callus induction (70%) on nodal explants was observed on OM medium containing 9.12 µM melatonin + 17.7 µM BAP under both dark and light conditions. The WPM containing the combination of BAP and melatonin 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.