Dear Anju.....I think Yes, Browning of calli is a problem in its further regeneration. I suggest to keep on subculturing or optimize concentration of antioxidants being added in media. I donot know about your crop and objective, but you can definitely control phenolics otherwise process will be halted or slowed badly.

Yes, browning of your cultured tissue is a problem and certainly hinders with its growth performance. therefore it is advisable to get rid of it ASAP. Also, a growing callus is visually different and shows soft, friable cell masses or shoots/organs (whatever the case may be).

Dear Anju

Oxidative browning is a common and severe problem in plant tissue cultures including callus cultures of some plant species, where browning is caused by accumulation and oxidation of phenolic compounds. Brown callus results in poor growth, eventually leading to cell death. Intensity of browning in callus could be decreased by adding a combination of 20-100 mg/l ascorbic acid and 10-50 mg/l citric acid to the medium.