The effect of thidiazuron level on in vitro regeneration type and peroxidase profile in Eucalyptus microtheca F. Muell more

The green twigs of 1-year-old Eucalyptus microtheca F. Muell seedlings were cultured on modified MS medium, supplemented with α-naphthalene acetic acid (NAA) and kinetin (Kin) hormones at 12 different concentrations. After 4 weeks, the combination of 1 mg l−1 NAA + 1 mg l−1 Kin induced the highest number of axillary shoots. Meanwhile, embryogenic calli were observed in media containing 4 mg l−1 NAA + 0.5 mg l−1 Kin, without any regeneration. The hormone treatments were followed by subculturing the twigs in different levels of thidiazuron (TDZ). The combination of 1 mg l−1 NAA + 1 mg l−1 Kin together with 0.01 mg l−1 TDZ resulted in an increase of direct shoot, while higher amounts of TDZ led to adventitious shoot induction. Somatic embryogenesis was observed in the treatment containing 0.01 mg l−1 TDZ + 4 mg l−1 NAA + 0.5 mg l−1Kin. The peroxidase (POD) band patterns in regenerated plantlets were investigated in order to determine the effect of different levels of TDZ on loci synthesis. A dimer locus, a tetramer locus and two epigenetic bands (a new band for NAA + Kin and the other for TDZ) were observed in the POD profiles. In case of low (0.01 mg l−1 and 0.1 mg l−1) levels of TDZ, one heterozygote allele was disappeared from dimer locus, while at higher TDZ levels, the dimer locus lost its stability and tetramer locus showed a high activity. Thus, POD allele patterns seems to be a feasible marker for different types of regeneration.