Domestication of Exacum trinervium

Abstract

Exacum trinervium (L) (Binara) (Gentianaceae) is one of the endemic rare plant species in Sri Lanka. Though the availability of these plants has restricted to certain areas of the country it can be used for both horticultural and floricultural purposes. The present study was conducted to investigate mass propagation methods for Exacum in order to introduce a novel ornamental species to the local horticultural industry. Explants were obtained from Pilikuththuwa forest reserve which located in Gampaha district, Sri Lanka. 20 % commercial bleach Clorox was applied for 20 minutes and 0.1 g/l mercuric chloride for 10 minutes application were selected as the most appropriate surface sterilization procedure for Exacum shoot tips, nodal segments and leaves. 10 % Clorox for 10 minutes was selected to surface sterilize Exacum seeds. Shoot tip explants were cultured on full strength Murashige and Skoog medium (MS medium, 1962) supplemented with 1.0 mg/l BAP. Cultures were maintained for two months and novel shoot clusters were separated and transferred to shoot multiplication medium, consists of MS basal medium supplemented with 3 % (w/v) sucrose, 2 mg/l BAP and agar 1 % (w/v). Exacum leaf explants were cultured on full strength MS medium supplemented with 1.0 mg/l NAA, 1 mg/l BAP and 3 % (w/v) sucrose. Exacum seeds were cultured on MS medium supplemented with 1.0 mg/l BAP. The seedlings were transferred to the multiplication medium after 30 days. MS basal medium supplemented with 3 % (w/v) sucrose, 2 mg/l BAP and agar 1 % (w/v) was used as the multiplication medium. Compared to the other explants (shoot tips and leaf segments) Exacum seed cultures produced a higher number of plantlets (200-300) per replicate.