eng Science and Education Publishing World Journal of Agricultural Research 2333-0678 2022-06-08 10 1 15 19 10.12691/wjar-10-1-3 WJAR20221013 article S.M. Waidyaratne sihini@pts.cmb.ac.lk 1 L.G.I. Samanmalie 2 P.K.C. Buddhinie 3 Department of Plant Sciences, University of Colombo, Colombo, 00300, Sri Lanka Plant Virus Indexing Centre, Department of Agriculture, Homagama, 10206, Sri Lanka Department of Botany, Faculty of Applied Sciences, University of Sri Jayewardenepura, Nugegoda, 10250, Sri Lanka In vitro plantlet regeneration ability of the local hybrid papaya variety Horana Papaya Hybrid 01 was evaluated using shoot tips from greenhouse-raised seedlings. Shoots tips surface sterilized in 20% Sodium Hypochlorite (Clorox®) for 20 min were established in Murashige and Skoog (MS) basal medium containing 6-Benzylaminopurine (BAP; 0.0,0.5,1.0,1.5 mg/L) in combination with 1-Naphthalene Acetic Acid (NAA; 0.0,0.1,0.5 mg/L) for shoot multiplication. Considering the high mean number of shoots per explant (4.8 ± 0.5) and absence of calli, 1.0 mg/L BAP was the best treatment for direct organogenesis. Proliferated shoots were transferred to a 1.5 strength MS medium containing 0.25 mg/L BAP and Gibberellic Acid (GA3; 0.0, 0.15, 0.30 mg/L) for further elongation. Elongated shootlets were placed in half-strength MS medium supplemented with Indole-3-Butyric Acid (IBA; 0.0,1.0, 2.0, 3.0 and 4.0 mg/L) for rooting. The highest root induction response (86%) and roots suitable for acclimatization were observed with 2.0 mg/L of IBA. Plantlets were acclimatized in poly cups containing a sterile potting mixture (soil, sand, compost, and coir dust; 1:1:1:1) and a survival rate of 75% was achieved under in vitro conditions. The findings of the present study can be optimized to develop a suitable in vitro micropropagation protocol for rapid clonal propagation of this papaya variety for producing true to type planting material. http://pubs.sciepub.com/wjar/10/1/3/wjar-10-1-3.pdf direct organogenesis hybrid micropropagation papaya shoot tip