Abstract
Sweetpotato [lpomoea batatas (L.) Lam. cv. Beniazuma] plantlets were cultured in vitro photoautotrophically (sugar-free medium) at two CO2 concentrations [(1500-1600 and 350-400 ?mol mol-1 (hereafter referred to as high and low CO2 concentration, respectively)] and two levels of photosynthetic photon flux (PPF) (150 and 75 ?mol m-2 s-1 hereafter referred to as high and low PPF, respectively) with the goal of determining suitable CO2 concentration and PPF as well as to identify a suitable low-cost root-supporting material. Three types of root-supporting materials, viz., Florialite (a mixture of vermiculite and cellulose fibre), perlite, and agar were tested. Enhanced growth of sweetpotato plantlets with a high photosynthetic rate in vitro was achieved with high CO2 concentration and high PPF regardless of root-supporting material. Whole-plantlet fresh mass was greater when the plantlets were grown with high CO2 and high PPF in Florialite followed by perlite and agar. Although the whole-plantlet fresh mass was lower in perlite than that in Florialite, it was similar to agar at similarly high CO2 and high PPF conditions. Use of high CO2 concentration and high PPF in the culture room will be beneficial for the uniformly better growth of the plantlets in large-scale micropropagation of sweetpotato. Substitution of perlite for agar as a supporting material will result in decreased production cost due to the low price of perlite, without losing the growth and vigour of the plantlets.
