HOW CAN DIFFERENT CYTOKININS INFLUENCE THE PROCESS OF SHOOT REGENERATION FROM APPLE LEAVES IN ´ROYAL GALA´ AND ´M.26´

Abstract

The effects of different types of cytokinins on the shoot regeneration from leaf explants of apple scion 'Royal Gala' and apple rootstock 'M.26' were evaluated. Regeneration media contained either thidiazuron (TDZ), or benzyladenine (BA), or meta-topolin (TOP), or zeatin (ZEA), or kinetin (KIN), or their N 9 -ribosides, respecttively, in the concentration range 0.5 to 8.0 mg L -1 . Effects of these cytokinins were evaluated on the percentage of regeneration (R%) and that of vitrification (V%) and on the number of regenerated shoots per explant (SN) and organogenetic index (OI) calculated from these data. The course of shoot organogenesis also was followed using stereomicroscope. Types and concentrations of cytokinins applied in the regeneration media influenced each parameter significantly and the regeneration answer was strongly genotype-dependent. The best regeneration (SN: 11.08, OI: 7.5) was achieved in 'Royal Gala' by using 0.5 mg L -1 TDZ. There was a clear relationship between the effect on the regeneration efficacy and the chemical structure of cytokinins considering classical cytokinins. In 'M.26' SN was the highest (3.22) using 6.5 mg L -1 BAR or 8.0 mg L -1 TOPR (3.18). SN was not significantly lower (3.12) by using 2.0 mg L -1 TDZ; however, OI was about half as big (0.63 compared to 1.29 or 1.74 with BAR or TOPR, respectively). 'Royal Gala' had higher organogenetic ability, than 'M.26': 3.5-fold higher SN and more than 4-fold higher OI was reached with this cultivar than with 'M.26'. Moreover, the similar developmental stage of shoots could be observed 3-5 days earlier than in 'M.26'.