Micropropagation of axillary shoots of Salix viminalis using a temporary immersion system

Key message Culturing axillary shoot explants of willow in liquid medium in plantform™ and RITA ® vessels increased the multiplication coefficient relative to that obtained by culturing the explants in semisolid medium in jars. Abstract A protocol for micropropagating willow by multiplying axillary shoots in liquid medium was developed, and the effects of the type of explant, medium composition, bioreactor type and frequency of immersion were investigated. The type of explant influenced shoot quality and the multiplication coefficient, with basal segments showing a higher capacity for proliferation than apical and mid-shoot segments. Hyperhydricity was not observed in shoots cultured with Murashige and Skoog medium with half-strength nitrates and supplemented with 0.22 µM BA and 3% sucrose. The willow shoots cultured in plantform™ and RITA ® vessels yielded higher multiplication coefficients than shoots grown in semisolid medium. High proliferation rates were obtained by immersion of shoots for 1 min three or six times a day, with additional aeration of 1 min per hour in the plantform™ bioreactors. Transfer to medium with 1% sucrose after 4 weeks of culture in medium with 3% sucrose increased the multiplication coefficient of basal segments cultured in RITA ® vessels, suggesting that the species could be micropropagated under photoautotrophic conditions. The willow shoots rooted spontaneously and were successfully acclimatized to greenhouse conditions. This is the first report of the use of a temporary immersion system to culture Salix viminalis . The study findings indicate the feasibility of the system as a method for the large-scale propagation of this species.