In vitro Plant Regeneration from Diploid and Tetraploid Exacum ritigalensis (Binara)

Purpose: Exacum ritigalensis (Binara/Ginihiriya) is an endemic plant found in Sri Lanka which has valuable ornamental characteristics. A protocol is timely important to develop for rapid, efficient multiple callus induction, shoot induction and rooting. Stem and leaf explants on Murashige and Skoog (MS) medium supplemented with different plant growth regulators were used for the study. The aim of the present study was to encompass the effects of plant growth regulators and explants on in vitro callus production, shoot regeneration and root formation of Exacum ritigalensis in diploid (28 n) and tetraploid (56 n) plants which have been exploited for genetic improvement programmes. Research Method: MS basal medium with 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, mgL-1 6-Benzylaminopurine (BAP) with 0.1mgL-1 2,4-Dichlorophenoxy acitic acid (2,4-D) were used to produce callus from aseptically produced stem cuttings and leaves. MS basal medium with 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, mgL-1 BAP and 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, mgL-1 Indole-3-butyric acid (IBA) were used for shoot and root induction respectively. Complete Randomized Design (CRD) with 10 replicates was used for each treatment and repeated the experiments five times. Findings: Results showed that stem cuttings were the best for callus induction compared to leaf explants of both diploid (1.4±0.1 cm2) and tetraploid (1.0±0.2 cm2) plant of E. ritigalensis within 19±2 days in MS basal medium supplemented with 2.0 mgL-1  BAP with 0.1 mgL-1  2,4-D.  The best mean number of shoot proliferation from callus (diploid = 16.0±1.0 and tetraploid = 11.5±0.5) and stem cuttings (diploid = 12.0±2.0 and tetraploid = 10.5±0.5) were observed on MS basal medium supplemented with 2 mgL-1 BAP with the highest shoot length. The highest number of roots (diploid =11.5±0.1 and tetraploid = 9.5±0.2) and root length (diploid = 3.2±1.7 cm and tetraploid = 2.2±0.3 cm) were observed on MS medium with 2 mgL-1 IBA. Research Limitations: Cytokinin (BAP) was used for induce both callus and shoot regeneration. Originality/value: The present study was developed a protocol for regeneration of diploid and tetraploid plants of E. ritigalensis.