Effects of different culture conditions (photoautotrophic, photomixotrophic) and the auxin indole-butyric acid on the in vitro acclimatization of papaya (Carica papaya L. var. Red Maradol) plants using zeolite as support
Plant regeneration of papaya via organogenesis and somatic embryogenesis has been successful; however, the biggest problem of in vitro culture of this species is the acclimatization of regenerated plants, where over 70% of the plants are lost before being planted in the field. Decreasing the relative humidity inside the culture vessel and thus increasing the ventilation, appears to have a greater effect on the adaptation of papaya plants, strengthening the function of the stomata and with this, allowing better control of water loss from the leaves. The aim of this study was to determine the effects of different concentrations of sucrose and indole-butyric acid (IBA) on rooting and in vitro acclimatization of plants using sterile zeolite as support and culture vessels with increased ventilation. Three concentrations of sucrose (0, 10 and 20 g L-1) were studied with and without auxin and as the control treatment, the rooting culture medium with agar during 17, 27 and 37 culture days. The highest percentage of rooting was recorded at 37 culture days in the treatment without sucrose and IBA with 80.0% and zeolite as support. The best photosynthetic values were achieved when in vitro shoots were grown in culture medium with auxin and different concentrations of sucrose, even though they were also high in the treatment without the presence of IBA and without sucrose at 17 days of culture. The combined effect of the zeolite, auxin (IBA), without sucrose in the culture medium and increased ventilation allowed photoautotrophic culture conditions which had effect of the increasing plant survival under ex vitro acclimatization conditions.
Key words: Carica papaya, photosynthesis, roots formation.