Shoot Regeneration and Plantlet Formation by Cascade Huckleberry, Mountain Huckleberry, and Oval-leaf Bilberry on a Zeatin-containing Nutrient Medium

Abstract

A plant regeneration protocol was developed for cascade huckleberry (Vaccinium deliciosum), mountain huckleberry (V. membranaceum), and oval-leaf bilberry (V. ovalifolium) clones. The effects of zeatin concentrations (0, 4.6, 9.1, and 13.7 μM) and explant type (leaf or stem segment) on adventitious shoot regeneration were studied on a nutrient medium of low ionic concentration. Adventitious bud and shoot regeneration was greatly influenced by clone, explant type, and zeatin concentration. Zeatin at 9.1 to 13.7 μM supported the best bud and shoot regeneration. At low concentrations (2.3 to 4.6 μM), zeatin enhanced shoot elongation and produced usable shoots after one additional subculture. The three clones differed significantly with respect to multiplication rate of adventitious shoots. Oval-leaf bilberry and mountain huckleberry clones produced six to seven 5-cm-long shoots per explant and cascade huckleberry clone produced five 3-cm-long shoots per explant, when 2.3 μM zeatin was used in the medium. Increasing the concentration of zeatin in the culture medium increased shoot number per explant, but decreased shoot height, leaf number per shoot, and shoot vigor. Proliferated shoots were rooted on the same medium but without any plant growth regulators (PGRs). Rooted plantlets were transferred to a 2 peat:1 perlite (v/v) medium for acclimatization and eventually established in the greenhouse with 75% to 90% survival rate. This in vitro protocol will be useful for micropropagation, in vitro selection, and genetic manipulation of Vaccinium species.