HIGH-EFFICIENCY CALLUS INDUCTION AND PLANT-REGENERATION IN PETIOLE CULTURE OF 4 POPLAR GENOTYPES

In order to develop a simple and feasible approach to achieve high fre quency plant regeneration for protoplast isolation and transformation experiments, a method was elaborated by using a new type of explant (p etiole segments) for the four Populus nigra genotypes. Callus initiati on from the petioles took place on N6 medium containing 2,4-D (0.1-1 m g/l). The highest rate of callus initiation (100%) was achieved when t he basic medium was supplemented with 0.5 mg/l of 2,4-D, in all tested genotypes. Far shoot regeneration, calli were transferred to MS and W PM medium supplemented with BA (1.0-2.5 mg/l) and NAA (0.2 mg/l). Mult iple shoot regeneration was observed in each shoot induction medium. T he highest rate of shoot regeneration (6.83 shoots/callus) was observe d on MS medium containing 2.5 mg/l BA and 0.2 mg/l NAA. The results sh owed highly significant differences between the media. There was no si gnificant difference between the genotypes and genotype x medium inter action.