Cytokinin and thiamine requirements and stimulative effects of riboflavin and α-ketoglutaric acid on embryogenic callus induction from the seeds of Zoysia japonica steud

Abstract

To enhance the embryogenic callus induction from the seeds of a recalcitrant turfgrass species Zoysia japonica , various supplements to the medium including cytokinins, vitamins, organic acids, and amino acids were tested. Both cytokinin and thiamine were found to be essential for stimulating embryogenic callus induction. Among the cytokinin and cytokinin-like compounds tested, BA and thidiazuron seemed to be the most effective. In the presence of cytokinin and thiamine, the addition of riboflavin or α-ketoglutaric acid proved to further enhance embryogenic callus induction. The addition of 0.1 mg/L BA, 4mg/ L thiamine and 100 mg/L α-ketoglutaric acid to the medium yielded a significandy increased embryogenic callus rate of up to 28.4 % per total calli induced. Thus, we show for the first time the necessity of thiamine and the stimulative effects of riboflavin and α-ketoglutaric acid on plant somatic embryogenesis.