Abstract
In this study, we compared the growth of Dioscorea cayenensis-rotundata (African yam) nodal segments, using semisolid medium in test tubes and liquid medium in 1-L Recipient for Automated Temporary Immersion (RITA((R))) temporary immersion bioreactors (TIB), and the application of various culture parameters. The addition of activated charcoal (AC) had a positive effect on the growth of nodal segments, both in semisolid medium and in liquid medium in RITA((R)) bioreactors. After 2 mo culture in the presence of AC, plantlets were 6.4-6.6 cm long compared to 3.2-3.8 cm in absence of AC, with no significant difference observed between the culture systems. In the range of inoculation densities tested (5-20 nodal segments per RITA((R)) bioreactor), there was no effect on the number of buds produced per nodal segment, the moisture content of plantlets (fresh weight basis), or on net fresh weight gain. By contrast, the individual leaf surface area of plantlets decreased in line with increasing inoculation density. Among the range of benzylaminopurine (BAP) concentrations tested (0-17.6 mu M), 0.44 mu M induced the highest number of buds (3.8 buds per nodal segment) in the TIB. However, comparable numbers of buds could be produced with media devoid of BAP, either by increasing the frequency of 1-min daily immersion cycles in RITA((R)) bioreactors from one every 12 h to one every 4 h or by using semisolid medium containing AC.