COMPARISON OF METHODS OF LIQUID-MEDIUM CULTURE FOR BANANA MICROPROPAGATION - EFFECTS OF TEMPORARY IMMERSION OF EXPLANTS

Five different liquid medium culture methods for meristem propagation of bananas were investigated and compared with solid medium culture. Treatments studied were: gelled culture medium (treatment 1); liquid medium with immersion of the plants (treatment 2); liquid medium with cellulose culture support (treatment 3); liquid medium with partial immersion of the plants (treatment 4); liquid medium aerated by bubbling (treatment 5); liquid medium with temporary immersion of the explants for 20 min every 2 h (treatment 6). After 20 days of culture, three culture groups with statistically different multiplication rates were observed: shoots in simple liquid medium and those on cellulose substrate proliferated little or not at all, shoots on gelled medium, those subjected to partial immersion and those in aerated medium displayed multiplication rates of 2.2 to 3.1, and the highest multiplication rate (>5) was observed in explants subjected to temporary immersion in the medium. Two groups of treatments differed in the accumulation of dry matter: the smallest weight (around 0.5 g) was observed in treatments 1, 2, 3 and 4, and accumulation was 2 to 5 times greater in the explants in aerated liquid medium and those subjected to temporary immersion. The highest multiplication rates and weight gains were observed in aerated treatments (treatments 4 and 5). Shoots in liquid medium continuously aerated by bubbling displayed hyperhydricity of the outer leaf sheaths. This was not observed with temporary immersion of explants.