Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 3, 2006
Publication Date: October 14, 2006
Citation: Sakhanokho, H.F., Pounders Jr, C.T. 2006. Evaluation of Growth Regulators on In Vitro Hibiscus Shoot Regeneration. Southern Nursery Association Proceedings vol. 51 pg. 346-349. Interpretive Summary: Hibiscus acetosella is native to western tropical Africa and consists of two variants, a red and green form. The red form, also known as ‘false roselle’ or ‘red leaf hibiscus’, shows resistance to insect pests and nematodes and is used as an annual ornamental grown for the attractiveness of its deep burgundy red, maple-like leaves. However, it tends to grow erect with little branching and very tall, easily reaching 8-12 feet, which can lead the stems to break. Therefore, development of a dwarf and compact form would be desirable. Genetic transformation has been used to induce dwarfism in several plant species. Such transformation, however, requires a dependable regeneration system. A transformation system based on somatic embryogenesis is ideal because it allows for the regeneration from callus of a single cell giving rise to a stably transformed plant. However, many plant species, in particular members of the Malvaceae family such as cotton and hibiscus, are recalcitrant to somatic embryogenic regeneration. Shoot apex regeneration is virtually genotype independent and has been used to regenerate many genetically engineered plant species. Growth regulators such as thidiazuron (N-phenyl-N’-1,2,3-thidazol-5-ylurea, TDZ) and 6-benzyladenine (BA) have been shown to induce multiple shoots from various explants. Induction of multiple shoots would help establish a more efficient mass micropropagation system and offer more explant targets for genetic engineering. The purpose of this study was to establish an efficient and reproducible multiple shoot regeneration system from shoot apices using growth regulators BA and TDZ. Sixteen different media containing various combinations of TDZ and BA were tested and produced multiple shoots. The medium containing 0.6 µM TDZ + 8.9 µM BA was one the best media, with 3.7 and 3.3 shoots per explant for the red and green variant, respectively.
Technical Abstract: Multiple shoot induction and plant regeneration was achieved from shoot apices in two genotypes (red and green variants) of Hibiscus acetosella Welw. ex. Hiern using the growth regulators thidiazuron (N-phenyl-N’-1,2,3-thidazol-5-ylurea, TDZ) and 6-benzyladenine (BA). Shoot apices were cultured for 30 days in 16 different media containing various concentrations and combinations of these growth regulators. Multiple shoot induction medium M9 (0.6 µM TDZ + 8.9 µM BA) was one the best performing media, producing 3.7 and 3.3 shoots per explant for the red and green genotype, respectively. Shoots elongated and acclimatized readily. Results reported here suggest that both BA and TDZ are directly involved in producing multiple shoots from the shoot apex of H. acetosella.