Plant regeneration of ‘Amethyst’ purple raspberry (Rubus occidentalis×R. idaeus‘Amethyst’) from in vitro leaf tissues

Abstract

Genotype-specific limitations in plant regeneration can greatly inhibit use of plant tissue culture and biotechnology in plant improvement. An experiment was conducted to discover the optimal plant growth regulator combinations for plant regeneration of a cold-hardy purple raspberry cultivar (Rubus occidentalis × R. idaeus 'Amethyst'). Regeneration of adventitious shoots was analyzed when in vitro leaf tissues were cultured on woody plant medium (WPM) with varying thidiazuron (TDZ) and indole-3-butyric acid (IBA) concentrations. The maximum regeneration rate occurred on WPM medium containing 1.0 μM TDZ and 0 μM IBA with an average of 93.3% of the explants forming shoots. The number of shoots produced from each leaf explant varied with the TDZ concentrations. An average of 3.9 shoots per explant was produced on 0.5 TDZ and 2.3 shoots on 1 µM TDZ medium. Higher TDZ or presence of IBA in the medium decreased the shoot number. Regenerated shoots were transferred to Murashige and Skoog (MS) medium with 1 to 10 μM IBA with or without polyvinylpyrrolidone (PVP) for in vitro rooting. More roots were induced in 10 μM IBA medium than lower amounts. Addition of PVP significantly enhanced rooting. Rooted explants were transferred to potting medium and grown in the greenhouse. This research will assist future raspberry improvement programs that use biotechnology techniques such as in vitro mutation and genetic transformation.