Somatic Embryogenesis and Plant Regeneration from Sorghum Meristem Explants without Intervening Callus Phase

Sorghum bicolor (L. Moench.) is considered as one of the crop species highly recalcitrant to tissue culture and genetic manipulation studies. During the last two decades several studies were done on sorghum somatic embryogenesis (SE) and plant regeneration, but the rate of plant regeneration was not sufficiently high and practical difficulties still exist in establishing and regenerating plants in a relatively shorter time period. The approach to regenerate the plantlets from somatic cells via intervening callus phase is time consuming and laborious which takes about 15-20 weeks. Hence an improved protocol using direct somatic embryogenic route of regeneration from shoot apices explants was developed. The shoot tips were cultured in the presence of Benzylaminopurine (BAP) and 1-Napthaleneacetic acid (NAA) at varying concentrations in Murashigeand Skoog (MS) media to determine the optimal media for SE as indicated by bulging of explants in the meristematic nodal region. The highest frequency of bulging (80%) due to SE was obtained on MS medium supplemented with 5.0 mgl-1 of BAP and 1mgl-1NAA.Further,plant regeneration could be directly induced from the bulged regions when supplemented half-strength MS media with Indole Butyric acid (IBA) and Indole acetic acid (IAA). Nearly 90% plant regeneration was achieved by using 2mgl-1of IBA and 0.5 mgl-1 of IAA. The well rooted plants are subjected to hardening and acclimatization in the glasshouse for 4 weeks. This rapid and efficient sorghum plant regenerative protocol described in this study is more useful for various genetic transformation studies.