Improved embryogenic callus induction and plant regeneration in big bluestem (Andropogon gerardii Vitman), a potential bioenergy feedstock
The objective of this study was to develop an efficient regeneration protocol in big bluestem, a potential feedstock that produces huge biomass. Embryogenic calli were induced from the seeds of cultivars, Kaw and Earl, on Murashige and Skoog (MS) medium with different concentrations of 2,4- dichlorophenoxyacetic acid (2,4-D) (0.2, 0.5, 1.0, 2.0, 3.0 and 5.0 mg l-1) alone or in combination with 6- benzylaminopurine (BA) (0.5 mg l-1) or L-proline (2.0 g l-1). In Kaw, the highest number of embryogenic calli (39.1%) was induced on MS + 0.5 mg l-1 2,4-D and L-proline, whereas in Earl, the highest number of embryogenic calli (39.8%) was obtained on MS medium containing 1.0 mg l-1 2,4-D and L-proline. The embryogenic calli were then transferred to regeneration media (MS medium supplemented with kinetin, 0.2, 0.5, 1.0, 3.0 and 5.0 mg l-1 or BA, 0.2, 0.5, 1.0, 3.0 and 5.0 mg l-1). Shoots were regenerated on all of the concentrations tested and the regeneration percentage and number of shoots per calli increased with the increase in BA or kinetin concentration. Regenerated shoots were transferred to half strength MS medium for rooting. The fully developed plantlets were established in the greenhouse. The regeneration protocol established in this study may be used for the application of genetic engineering technologies in big bluestem.
Key words: Big bluestem, biomass, embryogenic calli, L-proline, regeneration.