The paper describes in vitro culture protocol of floriculturally and medicinally important orchid Rhynchostylis retusa using leaves as explants. Leaf explants from 16-18 wks old in vitro cultures were inoculated on Mitra et al. (1976, M) medium supplemented with growth regulators such as auxins and cytokinins (2 mgl-1 each), both singly and in combinations. The regeneration response frequency and time taken for the development of plantlets varied with the growth stimulus. In the basal medium, the leaf explants remained recalcitrant to regeneration, turned brown, and perished within 40 days. Additional presence of AC in the medium proved effective for initiating regeneration response via callusing and PLBs formation, at the basal end. Presence of IBA, NAA, and IAA+KN in the medium proved ineffective for initiating regeneration response. NAA and KN (2 mgl-1) when used together in the medium, acted synergistically; cent per cent explants initiated regeneration response (8.75±0.25 days) via formation of callus, shoot buds and PLBs at abaxial and adaxial surface of leaf explants. Multiple PLBs were formed when the medium was augmented with KN. Development of PLBs with profuse growth of absorbing hair was observed in medium containing IBA+KN. Based on the present observations, basal medium supplemented with NAA and KN (2 mgl-1 each) is suggested as optimal nutrient medium for initiation, and multiple shoot formation via PLBs and healthy plantlet development.
https://doi.org/10.64873/JOSI.v35.i1-2.47-53