Micropropagation of Czech Apple Cultivars

The objective of this study was to investigate micropropagation protocols for use with three apple cultivars ('James Grieve Compact', 'Jarka' and 'Mivibe') bred in the Czech Republic. Apple shoot tips (5 to 10 mm in length) were established in vitro using 0.15% HgCl2 as sterilization solution. Contamination rate, survival and development of shoots from excised shoot tips were analyzed after sterilization. For the three cultivars, the effect of three growth regulators 1, 2 and 4 mg L-1 BAP (6-benzylaminopurine), 0.5 and 1 mg L-1 TDZ or 10 mg L-1 2iP in basal MS medium on proliferation, callus formation and shoot morphology is shown. Values of proliferation rate varied between 1.1 and 3.6. Generally, the highest rate was obtained for cultivar 'Jarka' that produced 3.6 new shoots on MS medium containing 4 mg L-1 BAP. The lowest number of newly formed shoots (1.1) was noted for cultivars 'James Grieve Compact' and 'Mivibe' on MS medium with low concentration of BAP (1 mg L-1). In vitro plants of ` James Grieve Compact' were of poor quality and developed symptoms of yellowing or chlorosis of leaves in later subcultures. It was possible to maintain actively growing in vitro cultures of ` James Grieve Compact' on all tested multiplication media only for a limited number of subcultures (usually, 8-9 subcultures; total culture period about 10 months), after which they either ceased to proliferate and multiply or eventually turned yellow-brown and subsequently died out. The effects of indole-3-butyric acid, indole-3-acetic acid or naphtalene acetic acid in concentration 1 mg L-1 on root induction were tested in MS medium for cultivars 'Jarka' and 'Mivibe'. Rooting was induced for both genotypes tested. However, the root induction was relatively low from 0 to 44% of in vitro rooted plants.