Optimization ofin vitro propagation ofPaulownia tomentosa

Paulownia tomentosa is very adaptable, widely distributed andextremely fast growing deciduous. The application of micropropagationtechniques in agro-forestry was essential because it offers a rapid wayof producing genetically uniform cloned stock with high quality. In order to study the effect of basal culture medium and growth regulatorson micropropagation of P. tomentosa, a factorial experiment wasconducted in a completely randomized design with four replications.The seeds were surface disinfected in a solution of 1.5% NaOCl for 10min and culture on MS medium containing 50 mg/l GA3. For shootmultiplication, isolated 1 cm long epicotyls were put on MS and DKWmedia supplemented with0.5, 1, 2 and 3 mg/l benzyl adenine (BA), 0.1mg/l NAA, 30 g/l sucrose, 7 g/l agar and pH = 5.6-5.8 beforeautoclaving. The subculture period was 4 weeks in growth chamberswith permanent temperature 25±1°C, white fluorescent light withintensity 3000 lx and 16:8 h photoperiod. Basal modified MS andDKW media (reduction of all macro elements by half) enriched with0.5, 1 and 2 mg/l indole butyric acid (IBA), 20 g/l sucrose and 7 g/lagar were studied for rooting efficiency. According to the results ofanalysis of variance, no significant differences were observed betweenMS and DKW media for multiplication and rooting traits. Due to thecompatibility of this species to environmental conditions, it seems thatthe same behavior was observed in tissue culture and showed the samereaction in both MS and DKW media for all traits. Mean comparison results showed that the highest shoot number (1.8-2.1 shoot perexplant) and shoot fresh weight (1.5-1.7 g) were obtained in mediacontaining 2 or 3 mg/l BA. The highest rooting percentage (100%), rootnumber (0.8 root per explant), mean root length (4.5 cm) and plantletfresh weight (2.9 g) were obtained in media enriched with 2 mg/l IBA.Rooted plantlets were rinsed with tap water to remove the mediumfrom the roots and transferred to the substrate of peat moss : cocopeat:perlite (2 : 2 : 1), treated with Mancozeb fungicide (0.2%) andcultivated for 30-40 days in growth chambers with gradual decrease ofthe atmospheric humidity. There is a significant positive correlationbetween root number as well as plantlet fresh and dry weight withex vitrosurvival. Acclimatization results showed that 90% of plantletssuccessfully survived after four months. The method described here canbe successfully employed for large scalein vitropropagation ofP. tomentosa plants.