Factors affecting bulblet growth of Lilium sp. in vitro and in vivo

Abstract

The major problem with in vitro propagation of lilies is small bulblet size, and the initial size of bulblets not only strongly affects growth and morphogenesis rates but also the transition between various vegetative and reproductive phases during development after planting. Therefore, bulblet growth is the most important factor in understanding how lily bulblets grow in vitro and the role of starch converted from sucrose in the medium on the growth mechanism in lilies, with the aim of revealing the effective in vitro culture condition to enhance in vivo performance of lily bulblets. The results of this study show bulblet growth correlates with the use of starch granule reserves inside explant tissue and in the medium. The main factor determining the growth of bulblets in vitro is explant size due to internal storage of starch, which plays a vital role in bulblet growth irrespective of cultivar. Furthermore, internal storage of sucrose plays a vital role and influences regeneration and bulblet growth in both in vitro and in vivo cultures. Therefore, the size of the bulblets produced in vitro strongly affects performance after planting. There is a high correlation (R= 0.9672) between bulb weight after the growth season and initial bulb weight and therefore, the ontogenetic age of bulblets at planting. Hence, culturing lily scale explants in a high sucrose concentration during regeneration of bulblets in vitro to increase bulblet size is the main point of interest for future production.