2018 ASHS Annual Conference

Lycoris is a bulbous plant of high medicinal, ornamental and ecological value; mainly distributed in East and South Asia. Lycoris has attracted the attention of synthetic organic chemists for their alkaloids that exhibit immunostimulatory, anti-tumor, anti-viral, and anti-malarial properties. Also, due to its distinctive flowers, Lycoris is a popular ground cover and cut flower crop. However, commercial Lycoris production and breeding have been hindered by its extended juvenile period and low regeneration rate under natural conditions. To date, no efficient regeneration system in Lycoris is available and the massive exploitation of bulbs has already caused considerable damage to wild resources and their natural habitats. In vitro propagation using different explants, including twin scales, multi scales, and floral organs, has had limited success. One factor hampering successful micropropagation of Lycoris might be the extremely high contamination rate. Another factor might be the difficulty in obtaining optimal explants since the accumulation and oxidation of phenolic compounds in mature tissues results in tissue browning and inhibited cell division. Here we established a bulblet regeneration system through direct organogenesis from the in vitro-derived probulbs of Lycoris sprengeri. The highest frequency (95.5±3.2%) of direct organogenesis was obtained on medium supplemented with 6.0 mg L^-1 6-benzyladenine (6-BA) and 1.0 mg L^-1 α-naphthaleneacetic acid (NAA), of which a mean of 36.3±6.8 regenerated bulblets per explant were obtained after 6 weeks of culture. Histological studies at different developmental stages revealed the mode of direct organogenesis from the probulbs. An increasing amount of cytoplasmically dense cells were observed to rapidly form adventitious meristems, which later gave rise to multiple shoot buds, suggesting direct organogenesis for bulblet regeneration via this system. The optimal medium for rooting was MS medium with 1.0 mg L^-1 NAA and 60 g L^-1 sucrose. More than 98% of rooted bulblets survived after acclimation. Based on the establishment of this bulblet regeneration system, multiple genetically identical clones can be generated from a single seed-derived probulb in a relatively shortened breeding cycle (approximately 20 weeks).