Contribution of sorbitol on regeneration of embryogenic calli in upland rice

Four upland rice cultivars were evaluated to determine the impact of 0, 10, 20 and 30 g L ^-1 sorbitol for callus induction and regeneration response on the MSB5 medium. These findings indicated that the incorporation of an appropriate amount of sorbitol significantly enhanced callus induction in only two of the cultivars, Kusan and Siam (10 g L ^-1). The positive effect of sorbitol was also detected in the regeneration experiment with all cultivars. The optimal level of sorbitol was 20 g L ^-1 for all of the cultivars except Selasi, for which 10 g L ^-1 led to the highest regeneration frequency. Interestingly, the addition of 20 g L ^-1 sorbitol in the culture media increased regeneration response (%) from 10 and 15 to 40 and 45 in Kusan and Siam, respectively (the low regeneration capacity cultivars). However, 30 g L ^-1 sorbitol decreased the response in both callus indication and regeneration frequencies in all tested cultivars.