In Vitro Morphogenesis of Woody Plants Using Thidiazuron

Abstract

Thidiazuron (TDZ) has been in use for in vitro shoot regeneration, in particular, recalcitrant woody perennials. Owing to its superiority over natural cytokinins in plant regeneration, TDZ has been the plant growth regulator (PGR) of choice for mature tissues. In majority of the tree species, TDZ has induced regeneration via axillary shoot proliferation, adventitious shoot organogenesis and somatic embryogenesis. Interestingly, TDZ has evoked different regeneration routes from the same explant at different concentrations. In addition, various other factors like pretreatment, explant type, maturity, orientation, TDZ concentration, combination with other PGRs and organic additives interact synergistically to promote shoot regeneration. Despite being potent PGR, supra-optimal level of TDZ produces shoot abnormalities like vitrification/hyperhydricity (stunted shoots) or fasciation (fused shoots). In shoot organogenesis and somatic embryogenesis, prolonged exposure to TDZ resulted in callus necrosis or reversal of shoot buds or somatic embryos to callus. Therefore, this review paper is intended to bring out the effectiveness of TDZ in woody plant tissue culture. The authors also emphasize on various interacting factors to minimize the negative consequences of TDZ treatment.