Embryogenic callus formation,growth and regeneration in callus and suspension cultures of Miscanthus x ogiformis Honda Giganteus' as affected by proline

The effects of proline additions to culture systems of Miscanthus x ogiformis Honda Giganteus' were investigated. Proline was added in concentrations of 0, 12.5, 25, 50, 100 or 300 mM to the callus induction and suspension culture media containing either Murashige and Skoog or N6 basal salts and 22.6 µM 2,4-dichlorophenoxyacetic acid. Shoot apices and leaves from in vitro-propagated shoots, and immature inflorescences from greenhouse-grown plants were used as explants for callus induction and formation. Suspension cultures initiated from embryogenic callus of immature inflorescences were used to test the effect of proline in suspension cultures. The proline additions affected the formation of embryogenic callus and the growth of suspension cultures. Improvements depended on the proline concentration and the basal salts of the medium. Addition of 12.5 to 50 mM proline to callus induction medium with Murashige and Skoog salts increased embryogenic callus formation on shoot apices and leaf explants while proline had no effect on embryogenic callus formation in medium with N6 salts. Increased growth with increasing proline concentration was obtained in suspension aggregates grown in medium with N6 salts, whereas proline only increased growth of suspension aggregates grown in medium with Murashige and Skoog salts at concentrations of 12.5 or 25 mM. A stimulating effect of proline on plant regeneration was observed in short-term cultures of callus as well as in long-term cultures of suspension aggregates. An optimum proline concentration for plant regeneration was found at 12.5 mM.