Investigating the relationships between callus browning in Isatis indigotica Fortune, total phenol content, and PPO and POD activities

Browning, as the most important problem to be solved in callus differentiation, occupies an important position in tissue culture. In this study, plant regeneration was induced using leaves from germinated Isatis indigotica Fortune seedlings and mature plants as explants. Activated carbon (AC) and a solidification agent (Phytagel) were added simultaneously to inhibit browning. We measured the total phenol content and the PPO and POD activities in callus-induced seedling leaves and mature plant leaves of different ploidy at various stages. The results demonstrated that single plant growth regulators could induce calli with higher rooting and browning rates. Despite the addition of AC and phytagel to the medium, half of the mature plant calli turned yellow and eventually died. The total phenol content and POD activity in calli from mature leaves showed significant differences within 0-4 weeks (P < 0.05) but were still higher than the biochemical parameters in calli induced from seedlings, while the PPO activity did not differ significantly (P > 0.05). Mature materials of different ploidy yielded similar results. The addition of 2 mg & BULL;L-1 BAP, 0.1 mg & BULL;L-1 NAA, and 1.5 mg & BULL;L-1 AC and solidification with 0.2% phytagel in MS medium resulted in the highest callus regeneration rate and the lowest browning rate. During dedifferentiation, the browning of the two may be associated with PPO activity and total phenol content. Key messageThe regeneration system of Isatis indigotica Fortune was optimized and the browning problem was solved. The browning of callus is related to PPO activity and the total phenol content.

Automated summary

This study optimized the regeneration system of Isatis indigotica Fortune and successfully solved the problem of browning in callus differentiation. The browning of callus is related to the activity of PPO and the total phenol content.