| Summary: | Seed germination problems of the new cut flower crop, Gentiana spp, generated the idea of gentian micropropagation by in vitro methods. The main objective of this research were to determine in vitro growth performance of shoots and roots of gentians in media containing different forms and levels of salts, vitamins, cytokinins and sucrose. Media investigated were MS medium, SH medium, woody plant medium (WPM), BS medium and LM medium. The cytokinins tested were BAP, kinetin, zeatin, TDZ and 2iP. Sucrose was chosen as the carbohydrate source in the media, with the effects of a series of concentrations examined on shoot proliferation and root initiation of G. japonica cv Royal Blue. The consensus medium formulated for shoot multiplication in this study combined WPM salts, BS vitamins, 0.5µM kinetin, 2% sucrose (w/v) and 0.55% agar (Davis) at pH 5.8. The importance of sucrose concentration was investigated during the in vitro rooting phase of Gentiana japonica cv Royal Blue. Root initiation decreased with increasing sucrose concentrations from 2% to 12% in woody plant medium (WPM). Medium containing 2% sucrose was superior for root initiation. Plantlets of G. japonica cv Royal Blue originating from 2% sucrose medium gave the highest survival rate and the most vigorous growth after transplanting to soil. To improve postharvest handling of Gentians, this study also investigated the effect of ethylene on G. axillariflora cv Akita Blue cut flowers. The leaves of Akita Blue could be injured by exposure to exogenous ethylene and the vase life shortened. The vase life of this flower crop could be promoted maximum by pulsing with 1mgl-1 silver thiosulphate (STS), an inhibitor of ethylene production, and/or 10% sucrose solutions. A modern technique in molecular genetics random amplified polymorphic DNAs (RAPDs) was used to derive relationships among five genotypes in this study. The genotypes were G. japonica cv Royal Blue, G. axillariflora cv Akita Blue, G. Sino ornata cv Alba, G. Antarctica and cultivar of unknown ...
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