Effect of nutritional and growth hormonal factors on in vitro regeneration of papaya (Carica papaya L. cv. Red Lady)

An efficient in vitro regeneration system was developed for the hermaphrodite papaya ‘Red Lady’ using nodal explants. Nodal explants were cultured on modified Murashige and Skoog (MS) medium supplemented with 3 6-benzylaminopurine (BAP) concentrations (0.0, 0.5 and 1.0 mgL^-1) or kinetin (10 mgL^-1) in combination with 1-naphthaleneacetic acid (NAA) (0.0, 0.1, 0.3, 0.4 and 0.5 mgL^-1). Media consisted of 0.5 or 1.0 mgL^-1 BAP in combination with 0.1 mgL^-1 NAA were determined to be the most effective based on the percentage of explants that produced shoots (93.33 and 86.67 % , respectively), mean number of shoots (1.79 and 1.81 shoots, respectively) and shoot height (2.26 and 1.95 mm, respectively). Shoot multiplication and elongation was achieved 30 days after transferring the initiated shoots to full-strength MS supplemented with 0.5 mgL^-1 BAP, 0.1 mgL^-1 NAA, and 200 – 400 mgL^-1 casein hydrolysate (CH). Effect of full and haft-strength MS medium supplemented with different indole-3-butyric acid (IBA) concentrations (0.0 – 4.0 mgL^-1) was tested for rooting. Adventitious rooting occurred after subculturing excised shoots on a medium containing 2.0 or 2.5 mgL^-1 IBA and 300 mgL^-1 CH, and plantlets were successfully acclimatised on potting medium consisting of peat moss: perlite (1:1). After 40 days of acclimatisation, plantlets grew normally and vigorously. This protocol can be used for commercial production of ‘Red Lady’ papaya plantlets.