Effects of silver nitrate on growth characteristics of micropropagated potato (Solanum tuberosum L.) plantlets

Abstract

Potato (Solanum tuberosum L.) is an economically important food crop and ranks only after wheat and rice in terms of productivity. Due to its increasing demand, there is need to increase its production. For potato crop improvement molecular breeding is one of the best method, by which genetically engineered better potato varieties can be obtained. The success of plant genetic engineering relies on several factors which include an efficient tissue culture system, for regeneration of plants from cultured cells and tissues. Growth and development of cells cultured in vitro are largely dependent on the presence of phytohormones, including ethylene in the culture environment. Ethylene produced by plant tissues grown in vitro may accumulate in large quantities in the culture vessels, and hence is likely to influence growth and development in such systems. Modifying the accumulation of ethylene in the head-space of culture vessels and altering its biological action are important in maximizing the desired de novo morphogenic pathway. Ethylene biosynthesis and action can be regulated by various methods. Silver ions treatment is one of the best chemical method, which inhibits its action by inhibiting its receptors. In most of plants, ethylene is perceived by a family of five membrane-bound receptors. The coordination of a copper ion with receptor is necessary for ethylene to bind, resulting in a conformational change of the receptor and the initiation of the ethylene signal transduction pathway. Interestingly, silver ions binds to the receptors in place of copper ion of ethylene, so ethylene responses block in the presence of silver. Many authors have reported the effectiveness of silver nitrate in tissue culture system. The objective of this study was to investigate the effects of varying silver nitrate concentrations (0.5, 1.0, 2.0, 3.0 mg L-1) on the growth characteristics of micropropagated microplants of six Indian and one exotic potato cultivars. The nodal shoot segments from each cultivar transferred on medium of all silver nitrate concentrations and after four weeks results collected. The common effects of silver nitrate were – (1) increases in leaf size, (2) reduction in shoot height, (3) reduced number of roots (4) promotion of root elongation and greening and (5) shoot and root colour became dark green and became thick also. Then these silver nitrate treated microplants transferred on MS-basal medium. It was observed that these silver nitrate treated