Somatic Embryogenesis in Papaya (Carica papaya L. cv. TNAU Papaya CO.8)

An efficient indirect somatic embryogenesis protocol for Carica papaya var TNAU Papaya CO.8 was developed using immature zygotic embryos as an explant. Two growth regulators namely 2,4-D and picloram each at 1, 2, 3 mg/L were tested for callus induction and the highest callus induction frequency (83.33%) was observed in MS medium supplemented with 3 mg/L 2,4-D. However the rate of conversion into somatic embryos was highest (63.33%) on MS medium supplemented with 2 mg/L 2,4-D. Maturation of somatic embryos was studied by using MS medium with different concentrations of abscisic acid (ABA) and benzyl amino purine (BAP) along with glutamine (400 mg/L). The maturation of globular embryos was observed to be higher in the combination of ABA (1.5 mg/L), BAP (0.4 mg/L) along with glutamine (400 mg/L). Even though regeneration was observed from cotyledonary stage embryos in presence of different growth regulators like BAP, α-naphthalene acetic acid (NAA), phloridzin dehydrate kinetin and gibberellic acid, further growth was not observed due to abnormal regenerative structures. Regeneration of cotyledonary stage somatic embryos were highest (77.4%) in half strength MS medium without growth regulators. The well-developed plantlets with shoots and roots were subsequently transferred for hardening.