Abstract
To characterize the germination behaviour of somatic embryos in date palm (Phoenix dactylifera L.), embryos derived from callus cultured on hormone-free medium were inoculated on full- or half-strength Murashige and Skoog (MS) medium supplemented with 0, 0.2, 0.4, 0.6, 0.8, and 1 mg l-1 naphthaleneacetic acid (NAA) or indole-3-butyric acid (IBA). The embryos either developed complete plantlets, or only shoots or roots. The results indicate a significant interaction between the experimental factors and response. Addition of IBA to the culture medium generally induced higher percentages of complete plantlets compared to NAA at any given concentration. The optimum treatment that maximized the percentage of complete plant formation (86%), consisted of half-strength MS medium containing 0.2 to 0.4 mg l-1 IBA. Somatic embryos that formed only shoots ranged from 2 to 26% and were associated with NAA-containing treatments. Generally, NAA enhanced the percentage of embryos that formed only roots, irrespective of medium strength, whereas IBA was inhibitory particularly on half-strength MS medium. Regardless of the germination treatment, 80% of plantlets (192 plants) survived in soil. This study demonstrates the possibility of reducing the length of tissue culture protocols for date palm by merging the germination (shoot formation) and rooting to a one-step procedure.