Influence of carbohydrate source, auxin concentration and time of exposure on adventitious rooting of the apple rootstock Jork 9

Abstract

Stem discs cut from micropropagated axillary shoots of the apple rootstock Jork 9 were used to study adventitious rooting in vitro. Different types, concentrations and combinations of carbohydrates, as well as different auxin concentrations and times of exposure to auxin were investigated to identify the optimal conditions for root differentiation. These studies demonstrated that sucrose (29–59 mM) promoted root formation but also callus formation. Sorbitol, on the other hand, required higher concentrations for optimum rooting, but reduced callus formation. Combination of glucose and sorbitol ( 117 59 mM ) or sucrose and mannitol ( 59 29 mM ) resulted in 100% root formation of cultured discs with more than six roots per disc. Also, with the combination sucrose/mannitol, the time required for optimum rooting was reduced compared to other combinations. An exposure of 540 min to 49.2 μM IBA in the presence of the sucrose/mannitol combination resulted in 100% of rooted discs, the highest number of roots per disc (6.55), and the lowest callus formation rate (4.40%).