In vitro shoot regeneration of Populus deltoides: effect of cytokinin and genotype.

Treatment differences were observed in the in vitro adventitious shoot regeneration response from internodal explants of three genotypes of Populus deltoides cultured on media supplemented with five concentrations each of the cytokinins 6-benzyladenine, 2-isopentyladenine, and zeatin. For each of the three genotypes, the greatest number of shoots were consistently regenerated on media containing the cytokinin zeatin. Tissue necrosis resulted when explants from any of the three genotypes were cultured on media supplemented with 6-benzyladenine. A zeatin concentration by genotype interaction was also observed. Genotypic differences in shoot regeneration were observed for 16 genotypes of Populus deltoides when cultured on medium supplemented with 0.5 mgL(-1) zeatin. Six genotypes were highly recalcitrant and failed to regenerate shoots. The percent of explants regenerating was greater than 50% for four genotypes.