2019 ASHS Annual Conference

Paulownia elongata is a fast-growing multipurpose tree. To assist commercial mass production, two week old rootless seedlings were placed in normal and inverted orientation in Murashige and Skoog (MS) and Gamborg’s B5 media (B5) with two carbon sources (30 or 40 g/L) and thidiazuron (TDZ) (25 µM) + Indole acetic acid (IAA) (5 or 10 µM) for shoot induction. Explants in normal orientation produced up to 39 shoots per explant after ten days in shoot induction medium, while only 28 and 12 for five and three days. For inverted explants, the shoot induction pattern was similar with respect to the induction days but number of shoots was much higher to 50, 47, and 37 in ten, five, and three days. For normal orientation explants, treatments MS+ 25 μM TDZ+5 μM IAA+maltose (40 g/L), B5+25 μM TDZ+5 μM IAA+maltose (40 g/L), and B5+25 μM TDZ+5 μM IAA+sucrose (30 g/L) with ten days shoot induction period resulted in high shoot numbers with no significant difference among three treatments. For inverted orientation explants, the medium, B5+25 μM TDZ+10 μM IAA+sucrose (30 g/L), for ten days should be recommended. Vegetative buds from mature trees were used as explants to develop in vitro stock in comparison with juvenile seedlings. After three weeks, nodes and petiole with half leaf were used as explants in B5 medium supplemented with TDZ (25 μM) and IAA (5, 10 or 25 μM) and maltose as carbon source (40 g/L). The highest number of shoots produced from nodes were 110 and 77 from petiole with half leaf. Petiole with half leaf was more responsive as compared to nodes. Heatmaps were generated to track the progress of each explant. Histological studies and scanning electron microscopy were used to document initiation of meristematic cells and shoot meristems. Elongated shoots with one to five nodes were transferred to MS basal and MS+5 μM IBA resulting in 100% rooting. Acclimated plants were successfully transferred to the greenhouse and had 60% and 70% survival rate for MS and MS+5 μM IBA respectively.