In Vitro Propagation of the P-HL Dwarfing Sweet Cherry Rootstocks

We have developed a rapid shoot multiplication procedure for in vitro propagation of dwarfing P-HL rootstocks ('P-HL A', 'P-HL B', 'P-HL C') for sweet cherries (Prunus avium L.). Shoot tips were successfully established in vitro and micropropagated on Murashige and Skoog (MS) based media containing different concentrations of 6-benzylaminopurine (BAP). Multiplication rates varied depending on the rootstock and concentration of BAP. The highest multiplication rate was obtained for 'P-HL A', yielding 10.9 +/- 0.5 shoots (>10 mm) on MS medium containing 1.5 mg L-1 BAP. The lowest multiplication rate was obtained for 'P-HL B', which yielded only 2.0 +/- 0.3 shoots on MS medium containing 0.2 mg L-1 BAP. The highest concentration of BAP (2 mg L-1) was deleterious to shoot growth and multiplication rate. The antibiotic cefotaxime (200 mg L-1) eliminated bacterial contamination during in vitro multiplication. Addition of indole-3-butyric acid (IBA) improved the in vitro rooting on modified MS medium.