Abstract

A micropropagation method was developed for a cold hardy purple raspberry cultivar (Rubus occidentalis × R. idaeus ‘Amethyst’). In vitro shoot cultures were initiated from shoot tips of a 30-year old ‘Amethyst’ plant. The effects of basal medium, plant growth regulator, and temperature on shoot proliferation were investigated. Shoots were produced from explants in both Murashige and Skoog (MS) and Driver-Kuniyuki Walnut (DKW) media supplemented with different concentrations of thidiazuron (TDZ) and benzyladenine (BA), solely or combined. One micro molar TDZ gave rise to the maximum proliferation rate. Interactions between BA and medium or TDZ were significant. Shoots produced on media with 1.0 μM TDZ had thick stems and small, dark green leaves whether BA was absent or present. Shoots can be rooted both in vitro and ex vitro with or without IBA at 0 to 1.0 μM. However, combination of rooting and shoot multiplication by adding a low level of TDZ to rooting medium produced multi-cane plants resulting in shortening propagation time, increasing survival rate, and lowering the production cost.