PROPAGACIÓN IN VITRO DE MIYAMASUKASHI-YURI (LILIUM MACULATUM Thunb. var. bukosanense), UNA ESPECIE VEGETAL AMENAZADA

Abstract

Lilium maculatum var. bukosanense (Honda) Hara, called Miyamasukashi-yuri in Japanese, is a wild lily, considered as critically endangered in Japan. Before L. maculatum var. bukosanense is lost, attempts for in vitro propagation can be performed to provide information for its rescue, efficient ex situ conservation as well as for possible use in breeding programs to be used as ornamental plant. For bulblet induction, five scales from aseptic bulbs were used for each treatment and placed in the MS (half-trength) medium, supplemented with sucrose 3 %, agar 0.8 %, at pH 5.8, and the effect of two plant growth regulators (PGR): α-naphthaleneacetic acid (NAA) at 0.0, 1.0, and 2.0 mg L^-1, in combination with thidiazuron (TDZ) at 0.0 and 0.5 mg L^-1, were studied. Two illuminating conditions (light or darkness), and the presence or absence of activated charcoal (AC) in the medium were also tested. A total of 16 treatments were tested. Explants cultured under light and AC did have a favorable effect on bulblet induction. The average number of induced bulblets under light condition was the double (4 per explant) than those induced under darkness, both in presence of AC, irrespective of PGR level. The best treatments were those with NAA 2 mg L^-1 + TDZ 0.5 mg L^-1, and without PGR, all of them with AC and under light. After 12 weeks of culture, an average of 2.4 well-formed bulblets was obtained per responsive explant. Six months after culture initiation, more than 640 regenerated plantlets from 320 explants, with roots and leaves were acclimatized and transferred to greenhouse conditions with 100 % success of survival. All the regenerated plantlets were morphologically similar among them, and had those characteristic feature of the flowers of this species. Moreover, no chromosome number (2n=24) variation was observed among scale-regenerated plantlets tested. The micropropagation procedure described here did not require a callus phase, thus we can state that the simple culture of scales could be applied successfully as a strategy for in vitro propagation in 12 months and thus contribute to the rescue and conservation of this plant species.