Effect of phloroglucinol on rooting and in vitro acclimatization of papaya (Carica papaya L. var. Maradol Roja)

The development of somatic embryogenesis in papaya (Carica papaya L.) on semisolid culture medium provides an alternative for propagation and breeding of this species. However, a critical factor in the protocol is the low survival of plants in ex vitro conditions. The aim of this study was to determine the effect of the product phloroglucinol on rooting and in vitro acclimatization of somatic embryo-derived papaya shoots using sterile zeolite. In vitro shoots were placed in culture vessels with phloroglucinol at 0, 79, 118.5, or 158 mu M with 9.8 mu M of indole-3-butyric acid and zeolite as a support on half-strength Murashige and Skoog semi-solid medium. Different morphological and physiological variables were evaluated after 27 d of culture. In the treatments with phloroglucinol, very good rooting development in shoots from somatic embryogenesis was achieved. The phloroglucinol stimulated the root elongation and formation of new roots with respect to the agar control. The best results for in vitro shoots were obtained with 79 mu M phloroglucinol plus 9.8-mu M indole-3-butyric acid, where 100% rooting, with 2.40-cm root length, 1.76 root number and the highest values of photosynthesis (6.497 mu mol CO2 m(-2) s(-1)) was achieved in 27 d of culture compared to the control. This facilitated a better survival rate state of plants (96.5%) in ex vitro acclimatization conditions.