Silver nitrate and 2-isopentyladenine promote somatic embryogenesis in date palm (Phoenix dactylifera L.)

Embryogenic callus derived from offshoot tip of date palm (Phoenix dactylifera L.) was transferred to MS medium containing 0, 25, 50, 75, or 100 μM AgNO₃ combined with 0 or 0.5 μM 2iP. Embryogenic callus weight, number of embryos developed and embryo elongation were significantly influenced by the interaction between silver nitrate (AgNO₃) and 2iP. In the absence of 2iP, callus weight was greatest with 75 μM AgNO₃, but in the presence of 2iP omitting silver nitrate resulted in the highest callus proliferation. The number of embryos increased in response to increasing silver nitrate concentration in the absence of 2iP, but in the presence of 2iP increasing the concentration of silver nitrate gave the opposite trend. The number of resultant embryos was the highest on 25 μM AgNO₃in the presence of 0.5 μM 2iP. This treatment also caused maximum embryo elongation. The results have shown that silver nitrate promoted callus proliferation and enhanced the formation and elongation of somatic embryos of date palm. Furthermore, the action of silver nitrate was clearly modified by the addition of 2iP. Depending on the response, 2iP modification ranged from slight alteration to complete inversion of the general trend associated with increasing silver nitrate concentration. The observed stimulatory action of AgNO₃ on date palm somatic embryogenesis may contribute to improve existing regeneration systems particularly for recalcitrant date palm genotypes.