Regeneration of Blueberry Cultivars through Indirect Shoot Organogenesis

Leaf explants derived from in vitro-grown shoots of blueberry cultivars Bluejay, Pink Lemonade, Sunshine Blue, and Top Hat were cultured on woody plant medium (WPM) supplemented with 9.12 mu M 6-(4-hydroxy-3-methylbut-2-enylamino)purine or zeatin (ZT) in combination with 1.23, 2.46, or 4.92 mu M indole-3-butyric acid (IBA). Calluses were induced from the explants and adventitious shoots were regenerated. 'Sunshine Blue' and 'Top Hat' produced more than four shoots per explant but shoot numbers were less than one for each 'Pink Lemonade' explant and about 0.2 per 'Bluejay' explant. The results indicate that there is significant difference among cultivars in indirect shoot organogenesis. The differences may be related to their diverse genetic background as they are polyploid hybrids. Microcuttings derived from adventitious shoots of 'Sunshine Blue' rooted in vitro in WPM medium supplemented with 9.84 mu M IBA and also rooted ex vitro in a peat-based substrate after cuttings were dipped or not dipped in IBA solutions. Direct rooting of microcuttings in the peat-based substrate was effective, suggesting that in vitro rooting may not be necessarily needed. Survival rate of ex vitro-rooted plants in a shaded greenhouse was high, more than 90%. The established shoot regeneration protocols could be used for rapid propagation of 'Sunshine Blue' and 'Top Hat' and for cultivar improvement through genetic transformation.