Rooting-enhancement of Rosa hybrida for tissue culture propagation

The effect of combinations of auxin sources and concentrations, temperature shifts, light intensity and light reduction on shoot-tips were studied relative to root formation of Rosa hybrida L. ‘Bridal Pink’ propagated in vitro. 2,4-dichlorophenoxyacetic acid alone was almost ineffective, and similarly its combinations with other auxins were less effective than other auxin combinations. While indolebutyric acid (IBA) alone did not stimulate rooting, both indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) were effective. Combinations of NAA and IBA and NAA and IAA were equally effective in stimulating rooting and also enhanced rooting more than IAA, IBA or NAA alone. When root quality is considered, the combination of NAA and IBA was better than that of NAA and IAA.An additive effect on rooting existed between NAA and IAA at most concentrations used. A similar effect was evident between NAA and IBA except when NAA was used at 0.025 mg/l, in which cases synergistic effects were observed. Light reduction to the rooting area, light intensities of 1.0 K lux or lower and holding the cultures for 1 week at 5°C all enhanced rooting.