Somatic embryogenesis has been obtained in many citrus cultivars. However, culture synchronization is yet to be achieved and in the present work we evaluate the effect of desiccation, cold and size of cell clusters on embryo production efficiency from callus cultures of Citrus sinensis L. Osbeck, cv. Valencia. The results showed that sieving was effective in promoting somatic embryo synchronization, whether or not it was followed by cold or desiccation treatments. Histological and histochemical analyses are presented to characterize the structure of cell aggregates and protein accumulation.

ABSTRACT The aim of this study was to establish the best concentrations of growth regulators for in vitro cultivation of jambu for a subsequent elaboration of an efficient micropropagation protocol. After sterilized, the seeds were inoculated on different media (MS, ½MS and water-agar) for in vitro germination. Nodal segments of in vitro germinated jambu seedlings were used as explants in the micropropagation with different concentrations of 6-benzylaminopurine (BAP) (0.0; 0.125; 0.25; 0.50 and 0.75 mg L-1) and callus induction with 2.4- dichlorophenoxyacetic acid (2.4-D) (0.0; 0.25; 0.50; 0.75 and 1.0 mg L-1) on Murashige & Skoog’s (MS) medium. The highest germination rates were obtained on MS medium with better seedling development and greater height (3.7cm). In micropropagation, the best treatment was obtained on 0.125 BAP (T2), with an average of 2.2 sprouts/explant, average height of 2.4 cm and vigorous sprouts. In callus induction, all treatments with 2.4-D had developed friable calluses in 30 days and using doses of 0.25 and 0.50 mg L-1 provided greater fresh matter. The induction of friable callus and the root production occur without supplementation of exogenous growth regulator.

Somatic embryogenesis has been obtained in many citrus cultivars. However, culture synchronization is yet to be achieved and in the present work we evaluate the effect of desiccation, cold and size of cell clusters on embryo production efficiency from callus cultures of Citrus sinensis L. Osbeck, cv. Valencia. The results showed that sieving was effective in promoting somatic embryo synchronization, whether or not it was followed by cold or desiccation treatments. Histological and histochemical analyses are presented to characterize the structure of cell aggregates and protein accumulation.