Most likely to be a problem of polyphenols, whose oxidation causes browning. This tends to inhibit further growth and necrosis sets in. Could also be due to senescence caused by ethylene production. You could  add silver nitrate to the MS medium at concentrations of  upto 50 micromolar. You could also explore the use of Silver Thiosulphate (STS) solution, made by mixing silver nitrate solution and sodium thiosulphate as recommended by Duchefa Biochemie

See info on https://www.duchefa-biochemie.com/product/details/number/S0536

Incidentally you could also try using  anti-oxidants in the medium, such as ascorbic acid or citric acid. These inhibit polyphenol oxidase enzymes. Another useful agent is Pollyvinylpyrrolidone (PVP).

Good work sir. Try replacing the carbon source and browning is the direct indication of Oxidation even due to Phenolic exudes. Try adding activated charcoal for a better performance or a bit concentration of PVP as mentioned by Mr. Eliud.

Thanks for your suggestions sir

Even frequent subculturing can also work in addition to ascorbic acid supply

do not MS medium. it will cause you in trouble. i will find the protocol for indica for you later 

I have seen considerable oxidation browning in some tree cultures I have worked with. If it is oxidation, you are likely to see browning in the media even before the callus turns brown. Is the media browning before the callus? If it is, I find moving the cuttings to new media after 48 hours removes any negative effects from oxidation. See this great review on the most up-to-date information involving preventing oxidation in tissue culture: 

Ahmad, I., et al. "Lethal effects of secondary metabolites on plant tissue culture." Am Eurasian J Agric Environ Sci 13 (2013): 539-547.

As for rapid browning (not caused by oxidation), I've seen this in cultures done by a student who did not properly dissolve her hormones in the media mixture. There was enough auxin to start callusing, but it was rapidly used up and the callus died quickly after. Perhaps your 2,4-D or BAP is contaminated or did not mix properly? Try dissolving BAP in a few ml of 1M NaOH before adding it to your media, it will make a more homogenous mixture.

Dear Prof. Weiya Xue ,

Thanks for your suggestion and I am waiting for your protocol

Hi Thriugnanasambantham,

Please see the attached paper about Indica rice tissue culture and transformation. In the paper, it describes 'callus browning' problem for Indica rice and how to minimize the problem (see the yellow highlights). They use N6D medium, and GelriteTM as gelling agent, instead of argar.

Why you are using maltose instead of Sucrose?

You can use salicylic acid to check oxidation and it also induces callusing, use above 2mg/l. It does work, have tried it.

There are so many compounds used for controlling browning in cultures 

PVP Activated charcoal Citric acid Silver Nitrate tru and standardize the type and concentration that suits your culture 

 here you go

http://link.springer.com/article/10.1007%2Fs00299-005-0100-7

I had the same problem in pearl millet (Pennisetum galucum). In monocots/grasses, sometimes reducing auxin source (2,4-D) helps in prevention of calli browning. Please reduced the 2,4-D from 3 mg/l to 0.5 mg/l (in media for subculture after calli induction). All the best! 

I assume that callus induction is being done in dark. Is it a new genotype for your experiment? Or ionic strength of the medium is on the higher side.

Hi did you manage to solve your issue?

Dear Ilakiya Kumar,

I followed the following procedure