Silver nitrate and putrescine enhance in vitro shoot organogenesis in polygonum tinctorium

Abstract

Polygonum tinctorium, also known as indigo plant, is widely distributed in Japan. Only few studies have investigated the regeneration of the indigo plant. The aim of this study was to develop an efficient protocol for shoot regeneration and shoot elongation. Shoot organogenesis and plant regeneration from internode explants of P. tinctorium were improved using the ethylene inhibitor silver nitrate (AgNO3) and the polyamine putrescine. Culturing of internode explants on initial shoot regeneration media (Murashige and Skoog media with 6-benzylaminopurine at 2 mg/L) supplemented with different concentrations (0, 1, 5, 7, 10, 20 mg L-1) of AgNO3 significantly improved the regeneration efficiency, resulting in higher number of shoots per explant and longer shoot length. The greatest number of shoots (7.2 ± 0.8) and shoot length (2.1 ± 0.1 cm) were obtained in media supplemented with 7 mg L-1 AgNO3, and further increase in the concentration of AgNO3 decreased the shoot production and shoot length. Additionally, we evaluated the effect of various concentrations (0, 10. 30, 50, 100, 200 mg L-1) of putrescine on shoot regeneration and shoot length. The highest number of shoots (7.4 ± 0.8) and longest shoots (2.2 ± 0.1 cm) were observed in cultures supplemented with 50 mg L-1 putrescine and further increase in concentration reduced the shoot regeneration and elongation. Our present study suggested that the addition of ethylene inhibitor AgNO3 and polyamine putrescine could be applied in micropropagation and plant transformation protocols of P. tinctorium.