In vitro culture initiation and regeneration of two highly productive clones of poplar

Abstract

In vitro shoot regeneration is a fast and reliable method for propagation of valuable tree genotypes and important step in genetic manipulations. This study aimed to establish an optimal in vitro culture initiation and regeneration protocol for highly productive poplar clones ‘Novoberlinska-3’ (Populus pyramidalis × P. laurifolia) and ‘Volosystoplidna’ (P. trichocarpa). In vitro culture was initiated either on MS (IM-MS) or WPM (IM-WPM) medium both containing BAP (0.2 mg.L^-1) and IBA (0.1 mg.L^-1). Results demonstrated that the best initiation medium for the clone ‘Volosystoplidna’ was IM-WPM on which 93.3 % of explants survived, while explants from ‘Novoberlinska-3’ better survived on IM-MS. After establishing both genotypes into aseptic culture, regeneration experiments were started using two types of explants, leaf and petioles, planted on callus induction medium containing 2iP (1.02 mg.L^-1) and NAA (1.86 mg.L^-1). Furthermore, microshoots were placed on shoot induction medium supplemented with 0.04 mg.L^-1 thidiazuron, and then transferred on shoot elongation medium with 0.2 mg.L^-1 BAP. Regeneration protocol showed better performance of poplar ‘Novoberlinska-3’, but it was also efficient for ‘Volosystoplidna’. Plant regeneration from leaf explants in the clone ‘Novoberlinska-3’ showed the highest regeneration percentage (92.3 %) and the number of shoots per explant (3.1), which significantly exceeded other explants. Our results showed a significant difference between the survivability of two clones during culture initiation. The differences in regeneration rates between the clones as well as leaf and petiole explants were also determined. Obtained aseptic cultures of highly productive poplar hybrids will be used in our further studies, especially for genetic transformation.