Effects of Silver Nitrate and Silver Thiosulfate on Growth Characteristics of Micropropagated Potato (Solanum tuberosum L.) Plantlets and Regeneration Efficiency of the Explants

Abstract

Potato (Solanum tuberosum L.) is an important food crop and ranks only after wheat and rice in terms of productivity. Current areas of research focused to improve the potato cultivars for various desirable traits such as disease resistance, improved yield and processing attributes etc. Due to heterozygosity, it is difficult to improve this crop through conventional breeding methods. Molecular breeding is one of the methods for potato crop improvement, through which the desirable traits can be introduced to potato cultivars. The success of plant genetic engineering depends on various factors such as an efficient tissue culture system for regeneration of plants using different explants. The growth and development of cultured-cells or tissues highly depend upon in vitro conditions that include the type of media, concentrations of various phytohormones and growth conditions. In closed-culture vessels, ethylene is produced by plant tissues that may accumulate in large quantities which is likely to influence growth and development. For maximizing the desired de novo morphogenic pathway, it is important to modify the accumulation of ethylene in the head-space of culture vessels and altering its biological action. There are various methods which can regulate ethylene biosynthesis and action. The addition of silver nitrate and silver thiosulphate in tissue culture medium are known to inhibit ethylene action by inhibiting its receptors. Ethylene is detected by a family of five membrane-bound receptors in most of plants. Ethylene signal transduction pathway is blocked by the silver ions by replacing the copper ions at ethylene receptors. In this study, we investigated the effect of silver ions on morpholological features of commercially important potato cultivars, Kufri Chipsona-1and Kufri Jyoti along with exotic cv. Desiree. For this purpose, we used different concentrations of silver nitrate (0.5, 1.0, 2.0, 3.0 mg L-1) and silver thiosulfate (1.5, 3, 6 and 9 μM L-1). Addition of silver nitrate resulted in stunted shoot length, increased leaf area and root length, thickening of shoots, shoots and roots became dark green. The effect on these growth features increased with increase in the concentration of silver ions. In case of silver thiosulfate, these growth features were not much affected at lower concentrations. This study helps us to compare the overall effects of silver nitrate and silver thiosulfate on growth characteristics of the potato plantlets. Moreover, Agrobacterium-mediated transformation was only initiated by introducing silver ions in the tissue culture media to see the effects during regeneration.