Auxins, Salt Concentrations, and Their Interactions during in Vitro Rooting of Winter-hardy and Hybrid Tea Roses

Abstract

Auxins, medium salt concentrations, and their interactive effects on rooting of two winter-hardy roses (Rosa kordesii Wulff `John Franklin' and `Champlain') and two hybrid teas (Rosa hybrida `John Paul II' and `Landora') were studied. The auxins (in mg·liter–1) IAA (0, 0.3, 1.5, 3.0, 6.0, or 15.0), IBA (0, 0.1, 0.2, 0.5, 1.0, or 3.0), and NAA (0, 0.1, 0.2, 0.5, 1.0, or 3.0) each were combined factorially with modified Murashige and Skoog (MS) medium (1/4, 1/2, 3/4, and full MS concentrations) and were tested for optimal rooting response. `John Franklin', `John Paul II', and `Landora' rooted well with low or no auxin and medium to high salt concentrations. Optimum rooting for `Champlain' was achieved with high IAA and low salts or with intermediate IBA and NAA concentrations and low to medium salts. The interactive effects of auxins and medium salts for `Champlain' showed that as salt concentration increased, the amount of IBA or NAA required for optimal rooting also increased. The effects of auxins and medium concentrations on root counts per shoot were similar to those for percent rooting. Adding auxin to the medium reduced root length for all cultivars, but salt concentration had a minimal effect. Roots generally were shortest at the highest IBA and NAA concentrations. Salt concentration had little effect on root length. Chemical names used: 1H-indole-3-acetic acid (IAA); 4-(3-indolyl)-butyric acid (IBA); α-naphthaleneacetic acid (NAA).