SOMATIC EMBRYOGENESIS IN CARICA PAPAYA THROUGH ZYGOTIC EMBRYO DERIVED CALLUS CULTURE

Abstract

A rapid and efficient system for papaya (Carica papaya L. cv. Co7) regeneration through indirect somatic embryogenesis has been established. Embryogenic calli were obtained from zygotic embryos (excised from 110-120 day-old fruits) on CIM [half-strength MS (Murashige and Skoog, 1962) basal salts and vitamins, 400 mg/L of glutamine, 6% sucrose, 4 g/L phytagel] supplemented with varying concentrations 0.5-12.0 mg/L of 2,4-D. The frequency of somatic embryo formation was as high as 54.35% when cultured on medium containing 2.0 mg/L of 2,4-D. Suspension cultures were superior to static cultures (solid medium) for the maturation of somatic embryos. Matured (cotyledonary stage) somatic embryos cultured on MSR medium supplemented with 0.4 mg/L BAP and 0.02 mg/L NAA showed regeneration efficiency up to 62.32%. The emerging shoots with 2-3 trilobed leaves were rooted on MSL medium containing 1.0 mg/L of IBA with efficiency of 60.07%. Plants with well-developed shoots and roots were subsequently hardened on a potting mixture enriched with arbuscular mycorrhiza. The plantlets from zygotic embryo explants were morphologically similar and normal. No phenotypic variations have been observed in field-established plants. This regeneration protocol assures a high frequency of somatic embryogenesis, maturation and regeneration into plantlets.