Optimization of plantain (Musa AAB) micropropagation by temporary immersion system

The positive and reliable effect of temporary immersion systems on in vitro shoot proliferation was already proved for different plant genera and it is now presented as an alternative for plantain micropropagation. Some culture parameters affecting the efficiency of the twin. asks system or temporary immersion bioreactor (Escalona et al., 1999) were investigated. Three different cytokinins (benzyladenine, thidiazuron and meta-topolin) were added to the culture medium and meta-topolin at a concentration of 4.4 mu M was proved to be the most efficient. Successive subcultures ( 28 days per subculture) were performed on medium supplemented with meta-topolin, revealing a decrease in multiplication after the 6th subculture. Multiplication rate was not changed within the ranges of immersion times ( 4, 12 or 22 min) and frequencies ( every 3, 5 or 7 h) tested. The size of the bioreactor ( 250, 1,000, 5,000 or 10,000 ml) and the volume of medium per inoculum ( 10, 20 or 30 ml) were also evaluated and appeared to have an influence on the multiplication. A proportion of 25 - 100 ml of headspace per inoculum and 30 ml of medium per inoculum resulted in a multiplication rate > 13 in 28 days.