Sachet,

Firstly, find that is your plant having any type of endophytic bacteria? may be it can grow and contaminate your culture. Secondly, try to identify that bacteria by a pathologist and add a suitable antibacterial agent to the media or treat the callus/explant with it before subculturing.

Also, go through following links which may be useful to you:

http://link.springer.com/chapter/10.1007%2F0-306-48099-9_12

http://www.academicjournals.org/article/article1380896695_Odutayo%20et%20al.pdf

https://www.ars.usda.gov/ARSUserFiles/4630/Contaminants/4.%20Plant%20Tissue%20Culture%20and%20Biotechnology%203%20137-142%20(1995)%20Bacteriology%20review.pdf

http://download.springer.com/static/pdf/775/art%253A10.1007%252Fs11240-014-0553-x.pdf?originUrl=http%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2Fs11240-014-0553-x&token2=exp=1482993167~acl=%2Fstatic%2Fpdf%2F775%2Fart%25253A10.1007%25252Fs11240-014-0553-x.pdf%3ForiginUrl%3Dhttp%253A%252F%252Flink.springer.com%252Farticle%252F10.1007%252Fs11240-014-0553-x*~hmac=2550d059b328651359ea954f7e6dd3b3ff03e696f41f2a9b70cb96080e7d87c4

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3371444/?report=printable

Based on the pink colour you might have a contamination with yeast. Will be difficult to get rid off with antibiotics. Does the infection come from the plant material, or the plates/vessels with medium you are using?

This pink color contamination isdue to  yeast not due to bacterial. This type of contamination also seen during apple mcropropagation.

Please find details:

Shoot cultures of apple cv. Pinova were contaminated with faint pink pigmented yeast. Yeast isolates were identified as Rhodotorula slooffiae with standard physiological methods and molecular analysis.

Decontamination of shoots was achieved using a combination of two treatments. Shoots were first soaked in half-strength Murashige and Skoog (MS) liquid medium containing silver nitrate (588μM) and Silvet 77 (0.01%) for 1–2h, and then transferred to a solidified MS medium containing both mancozeb (15mgl−1) and thiabendazole (40mgl−1).

Please read this article, Hopefully your problem will solve.

http://link.springer.com/article/10.1079/IVP2005647 

J. Kolozsvári Nagy, S. Sule, J. P. Sampaio.  Apple tissue culture contamination by Rhodotorula spp.: Identification and prevention. In Vitro Cellular & Developmental Biology - Plant, July 2005, Volume 41, Issue 4, pp 520–52

best regards

thank you @ Ashutosh Phatak and Rajesh Pati ji....

@ Eric van der Graaff- that I dont know ... probabally due to endophytic problems.

You could incubate the empty (no plant material on the medium) plates/vessels to see whether these are the source of the infection. I had this problem once, avoids spending time on trying to solve the 'wrong problem'.

Otherwise, when the yeast is always growing attached to the plant tissue you have an endophytic infection.

normally when I culture the new explants this problem was not there, but while subculturing it to new medium...normally with the induced direct shoots when it was subcultured to the other medium. this problem arises.

Yes, I am also agree with Eric van der Graaff statement.

Avoid to use fresh medium, You should use your medium after 3-4 days of preparation (or keep 2-3 plates/bottles in incubator). If there is any contamination in medium, its will be visible.

As per your ststement: contamination seen after subculturing.

May be there is 3 source of contamination

1- Medium

2- Improper handeling during culturing process

3- Contamination present inside explant (endophytic) from begning. and when it gets a suitable environment/ stage/ or any others factor, it comes out.

simple way to know contamination:

After Initiation,

1- if contamination is seen in medium but not on explant- Its means, The source of contamination is medium or improper handeling.

2-  if contamination is seen on explant but not on medium- Its means, The source of contamination is explant (may be two reasons; Either explants are not proper surface steriliszed and or Inborn contamination).

I am working in mango and apple, the contamination visible 3-4 moths after culture in same clean explant.

So betterway, discard contaminated cultures and initiate new one.

mine too having the same problem ji, from the feild explants it wont show any contaminations but after 3-4 months when it was subcultured then it will be contaminated with red/pink colonies.

thank you for the suggestions

Ralstonia Solanacearum, a bacterial pathogen, often gives red/pink coloured colonies.

Hope that helps!

thank you @ Ankita pandey ji

In fact, I have the same problem. I do the Agrobacterium rhizogenes mediated transformation to induce the hairy root in one medicinal plant. For the first step of co_culture, there is no contamination. However, after 4 days, I subculture in the new medium with cefotaxim (one kind of antibiotic), all petri plates became pink/red.

Could someone can give me some solution to solve this problem?

Thanks in advance!

For the problem of Le Thi Van Anh, With antibiotics in MS-media post co-cultivation with Agrobacs, there should though be lesser chances of bacterial Contamination, until the contaminant strain(s) have acquired drug resistance somehow, but that is rare. Either it could be yeast, as said already or might be the antibiotic is not working (Question is Agrobacterium dying with your cefotaxime ?)

For Sachet, Usually I get these contamination in my students' plates which are bacterial contaminants coming from under-sterilized forceps, scalpel, it might get colorful due to Fe (Iron) in the MS-media (as I tried to subculture these contaminants as streaks on LB later, but there was no colouring, try it if you could see retention of colour than being fascinated on these having some magical strains, or endophytes a du might be writing another proposal on it, Curiosity!!! as I see on your profile pic, spirit high), But sometimes you should just restrict to maintaining cleanliness and work on specific goals rather hitting on solving midway problems... I guess its all noscomial infections.

Try Try, Dig again... Good luck.

Many thanks for your advises. Finally, I could deal with the problem when I replaced carbenicilin to cefotaxim.

I am facing the same problem! thanks for the advice

Fabrics ji,

And all others

Thank you

Thank you Christian ji

I am researching the induce the hairy root in one medicinal plant. I have a very similar problem. Thank you for your answer

Dear Sachet Hegde the appearing of this kind of contaminant is highly frequent in TC. It could be of endophytic origin, but it could also appear because of wrong manipulation of aseptic cultures. Even some researchers have found that some kind of sporulant pink bacteria resist autoclaving.