High efficiency callus induction and plant regeneration in petiole culture of four poplar genotypes.

In order to develop a simple and feasible approach to achieve high frequency plant regeneration for protoplast isolation and transformation experiments, a method was elaborated by using a new type of explant (petiole segments) for the four Populus nigra genotypes. Callus initiation from the petioles took place on N6 medium containing 2,4-D (0.1-1 mg/l). The highest rate of callus initiation (100%) was achieved when the basic medium was supplemented with 0.5 mg/l of 2,4-D, in all tested genotypes. For shoot regeneration, calli were transferred to MS and WPM medium supplemented with BA (1.0-2.5 mg/l) and NAA (0.2 mg/l). Multiple shoot regeneration was observed in each shoot induction medium. The highest rate of shoot regeneration (6.83 shoot/callus) was observed on MS medium containing 2.5 mg/l BA and 0.2 mg/l NAA. The results showed highly significant differences between the media. There was no significant difference between the genotypes and genotype x medium interaction.