In vitro response of pistachio nodal explants to silver nitrate

The effect of silver nitrate on shoot differentiation and shoot growth was examined in order to improve the regeneration efficiency of pistachio (Pistacia vera L. cv. Kirmizi) in vitro. Nodal explants of in vitro-grown seedlings were used to test various concentrations and combinations of 6-benzyladenine (BA), kinetin (KIN), gibberellic acid (GA3) and silver nitrate (AgNO3). Addition of AgNO3 up to 48.0 μM to the culture medium improved the regeneration frequency and shoot growth, and reduced basal callus formation in all regenerated explants. The highest regeneration frequency (100%) was recorded on Murashige and Skoog (MS) medium containing 9.0 μM BA, 0.2 μM GA3 and 24.0 or 48.0 μM AgNO3 in combination. The best proliferation response in terms of both shoot formation and low callus production was obtained in the medium containing a combination of 9.0 μM BA, 0.2 μM GA3 and 12.0 μM AgNO3. Regenerated shoots, coming from three cycles of subculturing in proliferation media, were rooted in half-strength MS medium containing 12.0 μM indole-3-butyric acid (IBA). Well rooted plantlets were acclimatized and eventually established in peat and perlite. The development and optimization of an effective micropropagation protocol that is presented in this paper can give an important contribution to improve the quality of pistachio plants and, as a consequence, of orchard production in Middle East countries.