Development of culture medium for high density micropropagation of potato plants in vitro
AbstractAll commercial seed potatoes start off as small plantlets grown in tissue culture, and in vitro clonal micropropagation is the only way to ensure a constant supply of certified virus-free plants. Selecting the correct culture medium is one of the most important steps in developing a useful protocol for successful growth and propagation of plant species in vitro. In Alberta, all commercial tissue culture labs rely on the classic Murashige and Skoog (MS) medium to clonally propagate potato plants in vitro. Although MS composition is widely used as a standard growth medium, the nutrients it supplies may not be optimal for plant growth on an industrial scale. To meet the growers’ demand for seed potatoes, commercial producers have to grow plants at 4–10 times higher densities than those in research laboratories. The resulting plants are often of poor quality and exhibit reduced survival rate after being transferred to the greenhouse, thereby causing serious economic losses for the industry. Hence, the composition of MS medium likely requires major modifications to improve its efficiency for commercial use, particularly when potato plants are grown in culture vessels at high density and suboptimal culture conditions. The aim of this study was to evaluate the effects of additional MS nutrients on shoot quality and to determine the most critical culture medium components for improved plant growth response in potato. A factorial approach was used to test combinations of five nutrient factors: 1) NH4NO3, 2) KNO3, 3) mesos (CaCl2, KH2PO4 and MgSO4), 4) micronutrients (B, Cu, Co, I, Mn, Mo, Zn, Fe), and 5) source of carbohydrates. Each factor varied over a range of concentrations, added to MS medium. In total, 25 medium compositions were tested. The effects of these treatments on plant quality, such as shoot length, leaf size and color, were determined. An increase of mesos and micronutrients to concentrations four times higher than in the original MS medium was found to be the most significant factor associated with plant quality, multiplication and shoot length in all plants. This optimized growth medium can be used to produce higher quality potato plants in vitro.