Adventitious shoot regeneration from Sinningia speciosa leaf discs in vitro and stability of ploidy level in subcultures

Summary Leaf explants of Sinningia speciosa were cultured in vitro on Murashige and Skoog (MS) basal medium with various growth substances in order to regenerate shoots. On MS medium supplemented with indoleacetic acid (IAA) and kinetin, 80% of the explants produced green callus and 25 to 30 shoots with roots per explant. On MS supplemented with IAA and N⁶ benzyladenine (BA), 80% of the explants produced green callus and 40 to 50 shoots per explant but lacked roots. After 3–4 mo., these shoots were removed from the initial explants and transferred separately onto MS supplemented with indolebutyric acid for their elongation and successive rooting (3 mo.). Histological studies showed that the callus was associated with mesophyll cell layers, primarily with the spongy parenchyma. The shoots regenerated at the callus surface and were associated with newly differentiated vascular areas. Recurrent regenerations were obtained from leaf explants or apical meristems excised from shoots of the previous subcultures. These explants, as compared to initial cultures, had a high frequency of regeneration and also produced more shoots per explant. Chromosome numbers of root tip cells of the mother plant and of all in vitro-regenerated plants remained constant: 2n=26.