Improving In Vitro Plant Regeneration from Leaf and Petiole Explants of `Marion' Blackberry

Experiments focusing on plant growth regulators' concentrations and combinations, mineral salt formulations, and TDZ pretreatment formations were conducted to optimize in vitro shoot regeneration from leaf and petiole explants of `Marion' blackberry. Optimum shoot formation was obtained when stock plants were incubated in TDZ pretreatment medium for 3 weeks before culturing leaf explants on regeneration medium (Woody Plant Medium with 5 μ m BA and 0.5 μ m IBA) in darkness for 1 week before transfer to light photoperiod (16-hour photoperiod at photosynthetic photon flux of ≈50 μmol·m -2 ·s -1 ) at 23 °C ± 2 °C for 4 weeks. Under these conditions, ≈70% of leaf explants formed ≈40 shoots per petri dish that could be harvested and rooted to form plantlets. Chemical names used: N 6 -benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); gibberellic acid (GA 3 ); indole-3-acetic acid (IAA); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA); N-phenyl-N'-1,2,3-thidiazol-5-ylurea [thidiazuron (TDZ)].