In vitro flower induction in Gerbera (Gerbera jamesonii Adlam)

Gerbera (Gerbera Jamesonii Adlam) plantlets obtained from seeds grown on 1⁄4 strength Murashige-Skoog (MS) medium supplemented with 3% sucrose were multiplied on full-strength MS medium supplemented with 0.5 mg/l BAP and 3% sucrose. The individual and combined effects of sucrose concentrations (0, 1, 3, 5 and 8%), strength of the medium (full strength and half strength MS medium), and Gibberellic Acid (GA3) concentration (0, 1 and 5 mg/l GA3) on in vitro flower induction of multiplied gerbera plantlets were investigated. In vitro flower induction was achieved on full-strength MS medium containing 8% (w/v) sucrose and 5 mg/l of GA3 and 74% of the gerbera plants grown on this medium produced flowers. INTRODUCTION Gerbera (Gerbera jamesonii Adlam), commonly known as Barbeton daisies, belongs to the family Compositae (Asteraceae). This is a beautiful and popular flower in the cut flower industry and it possesses characters such as different colors, high productivity, flowering precocity and long vase life. Therefore, gerbera has very high demand, which is not fulfilled, both in the local and export markets. In the local market, the price of a single flower ranges from Rs. 10.00 to 20.00 and the price of a pot ranges from Rs. 150.00 to 200.00. Therefore, to cater to this huge demand, gerbera cultivation in Sri Lanka should be expanded to areas other than the upcountry, where gerbera is predominantly cultivated. However, gerbera requires specific climatic conditions such as low temperature (24C) for flower production and does not produce quality flowers when these requirements are not fulfilled. Therefore, it is essential to study the requirements for flowering of gerbera. Flowering studies face difficulties associated with the control of the environmental factors such as photoperiodism, vernalization, water stress and endogenous factors that control flower initiation in a natural environment. Thus, in vitro flowering techniques can be used in this situation to eliminate the difficulties related to flowering in natural environment. In vitro flowering is a novel technique in which the flowering process is induced by culturing whole plants, isolated organs or non-meristematic tissues in solid, semi-solid or liquid media under aseptic and controlled conditions. This technology helps to understand the physiological activities of the flowering process, which can never be performed under in vivo conditions (van Stadend and Dickens, 1991). In addition, in vitro flowering is a very important process in modern plant breeding techniques since it can be used for in vitro improvement through selective breeding methods as well as in in vitro seed production. 1 Department of Crop Science, Faculty of Agriculture, University of Peradeniya. In Vitro Flower Induction in Gerbera Furthermore, this technique allows a greater control of the whole part of the plant under investigation, the whole process can be linked to micropropagation techniques, more efficient application of exogenous substances can be achieved, effect or affected sites can be isolated or eliminated, and undesirable influences such as bacterial or fungal contaminations, wounded surface and organic substances under test can be avoided. Therefore, this study was conducted with the aim of investigating the possibility of using in vitro flowering techniques in identifying the factors such as C:N ratio and exogenous growth regulators, which influence on flower induction in gerbera. MATERIALS AND METHODS Plant materials Gerbera (Gerbera jamesonii Adlam) seeds were washed with water followed by mild liquid soap (Teepol). They were then sterilized with 10% sodium hypochlorite (NaOCl) with two drops of Tween 20 for 10 min. followed by another 10 min. with a fresh 10% NaOCl solution without Tween 20. The seeds were thoroughly washed with sterilized water and established on hormone-free 1⁄4 MS Macro nutrients (Murashige and Skoog, 1962) medium with 3% (w/v) sucrose. The seedlings obtained were multiplied on full strength MS medium supplemented with 3% sucrose and 0.5 mg/l Benzyl Aminopurine (BAP) by subculturing at eight-week intervals. The cultures were incubated at 16/8 h light/dark and 25C. After four subcultures, the plants were transferred to full-strength MS medium supplemented with 3% (w/v) sucrose without hormone and maintained for 8 weeks, to eliminate the effect of BAP, before being used for flowering studies Effect of sucrose concentration on in-vitro flowering of gerbera (Gerbera jamesonii Adlam) In vitro grown gerbera plantlets were established on MS medium supplemented with five different concentrations (0, 1, 3, 5 and 8% w/v) of sucrose to investigate the effect of sucrose concentration on flowering of gerbera. Each treatment was replicated four times and each replicate contained an average of 5 plants. Cultures were incubated at 25C and 16/8 h light/dark period and were maintained for five months by sub-culturing at four-week intervals on to the same medium. Performance of the plants was observed at two-week intervals. Data were recorded at the end of the experiment on length of shoots and roots, and number of leaves and plants. Data were analyzed using ANOVA and CATMOD procedure with SAS computer package Effect of the basal medium strength and gibberellic acid on in vitro flowering of gerbera (Gerbera jamesonii Adlam) Effect of full-strength and half-strength MS medium supplemented with 3% (w/v) sucrose combined with three different GA3 concentrations (0, 5 and 10 mg/l) on in vitro flowering of gerbera was investigated. Plants were sub-cultured on to the same media at four-week intervals. Performances of the plants were observed at weekly intervals and growth measurements (i.e. shoot and root length, number of leaves/plant, fresh and dry weight of shoots and roots) were recorded at the end of three months. Except the count data (number of leaves/plant) all the data were statistically analyzed by ANOVA (as a two factor