Sterilization of your explants for plant tissue culture is a very important step in creating cultures of viable productive vessels. There are many ways to go about sterilizing plant material to inoculate your cultures with a new plant. NaDCC is a very effective and affordable means for those that practice plant tissue culture at home or with a basic lab setup.
NaDCC is Sodium dichloroisocyanurate and commonly available as a pool chemical for disinfecting the swimming water. There are many places that sell this as a pool chemical and it is relatively easy to procure for sterilizing explants as well as other uses.
At room temperature NaDCC is stable but should be kept in a tightly sealed container. Mix solutions in smaller batches so that you can use them before they age too long and possibly lose some of their effectiveness. In dry powder form it is very stable and will last a long time if kept closed and dry.
NaDCC has a lower pH (somewhere around 6.8) in solution than regular bleach, making this a more effective disinfectant for the amount of chlorine. A solution with a PH around 12 is not as strong as the same at 6.8 PH. The reason is because the active ingredient is hypochlorous acid and works better in a more acid solution. A PH closer to 5.8 is preferable as the media protocol for most plants requires a 5.8 PH in the final media as it benefits nutrient uptake and the plants themselves better.
Phytotoxicity is generally low when using lower concentrations of NaDCC. A 500 PPM solution makes a good explant cleaner and is more gentle than bleach and alcohol. The best benefit from NaDCC is that a lower PPM can be used for an extended amount of time for heavily infected plant material. Since it is more gentle on the plant tissue, the plant material can be left in longer with the benefit of killing off more contaminates yet maintaining plant health.
“Solutions of sodium dichloroisocyanurate are more effective at high concentrations (5000 ppm) than a commercially available bleach for disinfection of shoot cultures. Sodium dichloroisocyanurate was also used at low concentrations (300 ppm) for longer periods (24 h-48 h) to disinfect shoot explants from the field, and was at least as effective for sterilization as a combination of Mercuric Chloride and Calcium hypochlorite.”
For disinfecting delicate plants like the traps from Venus flytraps and the pitchers from sarracenia a lower PPM of chlorine around 250 to 500 would be good. Rinse the explants in running tap water and place them in a tube with enough NaDCC solution to cover them generously. Add a drop of Johnson’s Baby Shampoo to act as a surfactant to get down to the plant’s surface and let them soak for as long as an hour or two as part of the sterilization process.
Older material that has been exposed to the outside may have a lot of contaminates on them. Hardwood cuttings when trying to use buds might be a good example of a time to use higher concentrations. For these applications you might use a concentration as high as 5000 PPM. Many plants don’t have protocols especially for NaDCC so some experimentation needs to be done regarding whether they will tolerate the 24 hour soak in NaDCC. It is worth trying on delicate and hard to sterilize material though.
250 ppm is good for a 24 hour soak which is better for more delicate explants or more contaminated but shorter times will also work well on lightly infested samples or very delicate plants. At 5000 ppm I wouldn’t recommend its use for more than an hour but that’s only because I don’t have experience with it for more than an hour on a stir plate.
After deciding whether you need a high or low concentration you must mix the NaDCC to a PPM (parts per million) that you plan on using. The first step is finding the concentration that is in the powder form you bought. There are several PPM levels you should investigate.
Frank Tromble from Root 66 Nursery explains to us how to mix your solutions to achieve the proper PPM (parts per million). Look at your package and find what the percentage of chlorine is for your pool cleaner you are using. Frank explains how to use the formula with the example of 96 percent chlorine in the product. Use that number on your package and go from there.
One tip that I learned from someone was to put a few drops on the surface of the medium at a concentration of about 25 ppm. This can be done when initially inoculating the vessel with the explant material or in the event that the ugly contamination rears its head in a vessel. It is worth trying before throwing the vessel out if it isn’t contaminated terribly. Autoclaving the NaDCC in the media may work but likely the heat will dissipate the strength or render it valueless.
One great technique that I employ is simply dipping in alcohol, then a quick 10 or 20 percent bleach solution. After that the material for the explant is moved to a 400 or 500 PPM solution and is not rinsed. Many plants have shown great results without rinsing in sterile water. This saves another step and makes culturing faster. It is a tool to consider to experiment with as time and effort saved can mean fewer contaminated vessels if done properly and successfully.
NaDCC is not an end all cure all solution to sterilizing explant material but it definitely has its merits and uses. It is easy to find and it is easy to work with. The powder mixes easily and stores easily as does the liquid solution. Dollar for dollar it’s a hands down contender with those practicing plant tissue culture at home or at the hobby level.
– by Edward Johnson