Propagation of Weeping Willow Trees (Salix babylonica L.) Using Plant Tissue Culture Technique

Abstract

This study was conducted in the Plant Tissue and Cell Culture Laboratory, Department of Forestry Sciences, College of Agriculture and Forestry, University of Mosul, during 2024–2025, aimed to establish an optimal in vitro propagation protocol for Weeping Willow (Salix babylonica L.) by evaluating four successive stages: initiation, multiplication, rooting, and acclimatization. In the initiation stage, single-node explants were surface-sterilized using commercial bleach (6% sodium hypochlorite) at concentrations of 5, 10, and 15%, combined with immersion times of 5, 10, and 15 minutes, then cultured on hormone-free MS medium. After four weeks, a 15% bleach concentration and a 15-minute immersion time each independently produced the highest rate of contamination-free explants (86%), confirming both factors as key contributors to effective sterilization. In the multiplication stage, single nodes (1 cm long) were cultured on MS medium supplemented with kinetin (Kin) at 0, 1, 2, 3, and 4 mg/L. After eight weeks, 1 mg/L Kin yielded the greatest number of shoots (6.4/node) and leaves (45.4/node), while the hormone-free control produced the greatest shoot elongation (5.4 cm), indicating a trade-off between cytokinin-driven proliferation and shoot length. In the rooting stage, shoots were cultured on half-strength MS medium with indole-3-butyric acid (IBA) at 0.0, 0.5, 1, and 1.5 mg/L; after six weeks, 0.5 mg/L IBA significantly outperformed other treatments, producing the highest root number (19.5/shoot) and root length (6.7 cm). During acclimatization, assessed four weeks after transfer to ex vitro conditions, 85% of auxin-treated seedlings survived regardless of IBA concentration, exceeding survival in untreated controls. Collectively, these findings establish a reliable, reproducible micropropagation protocol for Salix babylonica L.—combining 15% sodium hypochlorite for 15 minutes, 1 mg/L Kin, and 0.5 mg/L IBA—supporting efficient large-scale clonal propagation of this species for forestry and landscaping applications.