Developing an improved in vitro propagation system for slow-growing species using Garcinia mangostana L. (Mangosteen)

This investigation disclosed that evaluation of tissue culture parameters o f slowly developing species (e.g. Garcinia mangostana) requires monitoring of treatments through two or more successive, relatively long passages. Two 8-wk passages were necessary to observe differences in phytohormone effect s. Photoperiod and temperature effects were not clearly evident until tissu es had been cultured through three passages; the optimal photoperiod and te mperature for shoot proliferation could not be established until after the fifth passage. Our investigation revealed that no auxin supplementation was necessary for bud primordium differentiation in cotyledon explants or prol iferation of regenerated shoots. The optimum N-6-benzyladenine concentratio n for primordium differentiation was 13.3 muM, and for shoot proliferation ranged from 4.4 to 13.3 muM. Continuous culturing in an 8-h photoperiod at 30 degreesC resulted in progressively intensified degeneration of shoots af ter three passages. In contrast, successive passages in a 16-h photoperiod/ 26 degreesC regimen enabled sustained regeneration of shoots. The shoots ro oted at a rate of 85% when precultured for 3 d in a medium containing 4921. 3 muM indole-3-butyric acid, or 10 d at 492.1 muM, then cultured for two 8- wk passages in phytohormone-free medium. Following acclimatization by gradu ally lowering the relative humidity in the growth chamber, rooted shoots su rvival transfer to the greenhouse at a rate of 95%.