In Vitro Propagation of Dendrobium chrysotoxum (Lindl.)

In vitro asymbiotic seed germination of Dendrobium chrysotoxum varied with fruit harvesting time and culture medium used for germinating seeds. Seeds at different developmental stages were harvested and cultured on five asymbiotic orchid seed germination media i.e. defined and undefined media, namely 1⁄2 MS, KC, M, MS and PDA. Seeds harvested 220 days after pollination showed maximum germination on all media tested. Amongst the five basal media screened, 1⁄2 MS + 3.0% sucrose was the most effective followed by M, KC, MS and undefined medium PDA. Seedlings were formed within 12.35 ± 0.12 weeks. Besides fruit harvesting time, the effect of BA, KN and -naphthalene acetic acid (NAA) at 1 mg l each, singly and in combination in 1⁄2 MS medium + 3% sucrose (as basal medium), on seed germination and development of seedlings was also assessed. NAA proved optimal for germination and led to early seedlings formation within 10.25 weeks. BA/KN lowered the germination frequency and delayed seedling development whereas their combination with NAA could elevate % seed germination. The efficacy of growth supplements such as banana homogenate (25, 50, 75 g l) and peptone (1.0, 1.5, 2.0 g l) was tested on multiplication of cultures (at the protocorm stage) in 1⁄2 MS medium. Seedlings regenerated on all medium combinations, but greatest in organic growth supplemented medium. Protocorm segments formed shoot buds which eventually differentiated into shoots with no intervening callus stage. Among the treatments, highest regeneration frequency, a maximum of 9 shoots/explant, and their accelerated development into plantlets was supported by peptone (2 g l). Robust shoots and root formation was observed with banana homogenate (50 g l). A higher concentration of banana homogenate (75 g l) was detrimental to culture survival. _____________________________________________________________________________________________________________