© 2006 Heron Publishing—Victoria, Canada
In vitro regeneration of Salix nigra from adventitious shoots
Satu Lyyra (1, 2), Amparo Lima (3) and Scott A. Merkle (1)
1. Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602, USA / 2. Corresponding author (satu.lyyra@iki.fi) / 3. Department of Plant and Microbial Biology, University of California, Berkeley, California 94720–3102, USA / Received June 9, 2005; accepted September 2, 2005; published online April 3, 2006
Summary
Black willow (Salix nigra Marsh.) is the largest and only commercially important willow species in North America. It is a candidate for phytoremediation
of polluted soils because it is fast-growing and thrives on floodplains throughout eastern USA. Our objective was to develop
a protocol for the in vitro regeneration of black willow plants that could serve as target material for gene transformation.
Unexpanded inflorescence explants were excised from dormant buds collected from three source trees and cultured on woody plant
medium (WPM) supplemented with one of: (1) 0.1 mg l–1 thidiazuron (TDZ); (2) 0.5 mg l–1 6-benzoaminopurine (BAP); or (3) 1 mg l–1 BAP. All plant growth regulator (PGR) treatments induced direct adventitious bud formation from the genotypes. The percentage
of explants producing buds ranged from 20 to 92%, depending on genotype and treatment. Although most of the TDZ-treated inflorescences
produced buds, these buds failed to elongate into shoots. Buds on explants treated with BAP elongated into shoots that were
easily rooted in vitro and further established in potting mix in high humidity. The PGR treatments significantly affected
shoot regeneration frequency (P < 0.01). The highest shoot regeneration frequency (36%) was achieved with Genotype 3 cultured on 0.5 mg l–1 BAP. Mean number of shoots per explant varied from one to five. The ability of black willow inflorescences to produce adventitious
shoots makes them potential targets for Agrobacterium-mediated transformation with heavy-metal-resistant genes for phytoremediation.
Keywords:
black willow, phytoremediation, thidiazuron (TDZ), tissue culture.
