Differential Influence of Growth Regulators during Somatic Embryogenesis of Gynodioecious Papaya Varieties‘CO.7’ and ‘Red Lady

The study involved two auxins viz., 2,4-D (2,4-Diclorophenoxyacetic acid) and picloram at three different concentrations (1,2, 3 mg/L) in full strength MS media to study their comparative influence on induction of somatic embryogenesis from immature zygotic embryos of two gynodioecious varieties of papaya ‘CO.7’ and ‘Red Lady’. In papaya cultivar ‘CO.7’, 2,4-D at 2 mg/L gave the highest callus induction frequency of 90.93%, whereas comparatively higher concentration of 3 mg/L 2,4-D was found suitable for ‘Red Lady’ (87.26%). Although there was profuse callus formation, 2 mg/L 2,4-D recorded comparatively higher frequency of embryogenic calli in ‘Red Lady’ (51.67%) when compared to ‘CO.7’ (30.00%). Somatic embryo maturation was achieved upon transfer of embryogenic calli exhibiting globular stage embryos on to maturation medium (MS medium + ABA (Abscisic acid) and BAP (Benzyl amino purine) in different concentrations + glutamine 400 mg/L). In the maturation medium, the combination of 1.5 mg/L ABA and 0.4 mg/L BAP registered better conversion of the globular embryo to cotyledonary embryos than other levels. The frequency of somatic embryo germination was higher in ‘Red Lady’ (50.00%) as compared to ‘CO.7’ (31.67%) on half-strength MS medium devoid of growth regulators.