Plant tissue culture studies in Sorghum bicolor: immature embryo explants as the source material

Sorghum is a wonder crop from physiological point of view. It is the most important cereal crop, after rice and wheat.  The number of reports describing the use of transgenic Sorghum for basic studies in Biotechnology is still limited when compared to other crops. In one hand, the success of the transformation techniques is mainly dependent upon the availability of optimal protocols for highly efficient tissue culture techniques. On the other hand, regeneration in Sorghum is difficult. Hence, in this study an efficient and reproducible method for in vitro development of embryogenic callus and regeneration in Sorghum bicolor was developed. Immature embryo explants of Sorghum bicolor were cultured on MS nutrient medium supplemented with different concentrations and combinations of auxins and cytokinins.  Embryogenic callus was initiated on MS medium supplemented with 2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/l Kinetin (KN).  Addition of KN to MS medium containing 2,4-D  resulted in a significant enhancement on embryogenesis of the embryos. Amino acids also supported an improved frequency of embryogenesis. Therefore induction of a high frequency of somatic embryogenesis in immature embryos on MS medium is possible. Development of embryogenic callus, induction of somatic embryo and subsequent shoot regeneration was proficient at a concentration of 2 mg/l BAP. The regenerated shoots readily rooted on half strength MS medium supplemented with 1 mg/l naphthalene acetic acid (NAA). The regenerated plantlets were successfully transferred to soil and subsequently plants produced seeds. There was no difference between the acclimatized plants in comparison with in vivo plants in the respect of morphological characters.