Micropropagation of red and black chokeberry (Aronia spp.)

Aronia arbutifolia (L.) Pers. (red chokeberry) and A. melanocarpa (Michx.) Elliot (black chokeberry) are native shrubs with white spring flowers; dark, glossy, green foliage; red fall color; abundant fruit; pest resistance; and easy culture. Improved forms of Aronia, such as A. arbutifolia ‘Brilliantissima’, must be propagated vegetatively to maintain phenotype. Although Aronia spp. can be rooted from cuttings, propagation of new selections could be achieved more rapidly using micropropagation methods. We have determined that commercial multiplication of improved forms of Aronia by micropropagation is feasible. Shoot-tip explants, 2 to 3 cm long, were collected from actively growing, mature-phase tissue of a selection of A. melanocarpa and from A. arbutifolia ‘Brilliantissima’. Explants were prepared and surface sterilized as described by Brand and Lineberger (1986). Shoot tips were then placed on MS medium (Murashige and Skoog, 1962) (pH 5.7 before autoclaving) containing 3% sucrose, 0.65% agar (Sigma, St. Louis), and 4.4 μM N -(phenyl-methyl)-1 H -purine-6-amine (BA). Explants were subcultured three times at 4week intervals before being used for in vitro production of shoots. All cultures were grown initially in 25 × 150-mm culture tubes sealed with clear polypropylene caps and in 140-ml jars sealed with B-caps (Magenta Corp., Chicago) for the last subculture. The tubes contained 15 ml of medium and the jars 30 ml. The environment for all experiments was 24C ± 2C and 16 h of cool-white fluorescent light (40 μ m o l · m -2· s-1) . Shoot proliferation was evaluated on MS medium and WP medium (Lloyd and McCown, 1980) (pH 5.2 before autoclaving) containing 3% sucrose, 0.65% Sigma agar, and 0.0, 0.4, 2.2, 4.4, or 11.1 μM BA. Single shoots, 25 mm in length, were placed vertically in culture tubes on each combination of components. Shoot proliferation was evaluated after 8 weeks of growth. For rooting experiments, all microcuttings were harvested from cultures grown for 16 weeks on MS medium that contained 4.4 μM BA. For in vitro rooting, 25-mm-long microcuttings were individually placed on 15 ml of half-strength MS medium that contained 4.9 μM indole-3-butyric acid in 25 × 150-mm culture tubes. Microcuttings rooted under nonsterile conditions were planted in a moistened 3 milled sphagnum moss : 1 fine perlite (v/v) mix in 20 × 15 × 8-cm clear plastic trays at a density of 40 microcuttings per tray. Rooting was evaluated after 6 weeks. Rooted microcuttings were acclimated to greenhouse and outdoor conditions by gradually increasing light and reducing humidity (Brand and Lineberger, 1986). Both Aronia spp. initiated shoot proliferating cultures easily from actively growing shoot tips. The most shoots that could be used as microcuttings (8.8 and 5.6 for A. arbutifolia ‘Brilliantissima’ and A. melanocarpa, respectively) were produced on MS or WP medium containing 4.4 or 2.2 μM BA. Microcutting leaf expansion was enhanced on MS medium. Microcuttings of both Aronia spp. rooted readily, even on basal medium. Rooting percentages for A. arbutifolia ‘Brilliantissima’ were 87% and 96% (in vitro and nonsterile conditions, respectively) and 83% and 95% for A. melanocarpa. Rooted microcuttings were easily acclimated to greenhouse and then to outdoor conditions. More than 400 micropropagated A. melanocarpa plants were grown in 4.25liter containers; 3 months after rooting, most plants were 30 cm tall, had five to seven main branches, and were phenotypically identical to the original plant.