Thursday, August 11, 2016
Georgia Ballroom (Sheraton Hotel Atlanta)
Phalaenopsis is currently the most popular floral crop in the world; the high demand for plant supply is met through tissue culture. During its in vitro propagation, lower leaf yellowing in Phalaenopsis plantlets was observed in some susceptible cultivars. This study investigated its potential causes in regard to medium composition. Plantlets of Phalaenopsis Brother Pico Bahama ‘E.G’ were subcultured with four basal media, namely half-strength Murashige and Skoog (1/2 MS; control), Hyponex #1 at 3 g·L-1 (HP), Hyponex #1 at 1.5 g·L-1 + Peters Excel 15-5-15 Cal-Mag at 1.5 g·L-1 (HP-PE), and Peters Excel 15-5-15 Cal-Mag at 3 g·L-1 (PE). HP resulted in the most severe leaf yellowing, with 2.0 yellowed leaves per plantlet against just 0.3 in the control group. The number of yellowed leaves decreased as concentration of Hyponex decreased, which was 2.0, 1.1, and 0.6 for the HP, HP-PE, and PE, respectively. The ethylene concentration in the culture vessel corresponded to the severity of leaf yellowing, with highest ethylene concentration in HP (14 nL·L-1) and lowest in 1/2 MS (7.2 nL·L-1). The incorporation of organic additives (i.e., apple, banana, or potato) into the culture medium also resulted in more yellowed leaves and higher ethylene concentration in the vessel. For the tissue culture of Phalaenopsis cultivars that are prone to lower leaf yellowing, it is thus suggested to reduce the use of Hyponex #1 and certain organic additives.