Bioreactors for the rapid mass micropropagation of yam

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Morufat Balogun, m.balogun@cgiar.org

The tissue culture technique using meristems followed by serial nodal cultures can be effective for producing high quality seed yam but its use is limited by the slow rate of regeneration and propagation in a conventional semi-solid culture medium. Conventional tissue culture employs manual introduction into culture vials. However, the slowness of yam propagation in vivo also occurs in vitro where cultures for some genotypes can take more than 1 year to regenerate from meristems. This low multiplication rate limits the use of in-vitro produced plantlets; there are also losses during acclimatization and transplanting. Other limitations resulting in low propagation rates are frequent sub-culturing which increases labor costs, culture container size (hence nutrients), and sub-optimal culture aeration and uptake (Cabrera et al. 2011).

As part of its objective to develop technologies for the high ratio propagation of high quality seed yam, YIIFSWA is set to standardize in vitro propagation techniques using conventional and temporary immersion technologies. In most crops tested (pineapple, cocoa, potato, and others), the Temporary Immersion Bioreactor system (TIB) increased propagation rates (Watt 2012) through culture aeration combined with automation, both of which increase productivity.

The TIB technology involves the timed immersion of plant tissues in a liquid medium to allow for the aeration of cultures. Each unit is a bioreactor—an enclosed sterile environment provided with inlets and outlets for air flow under pressure—and therefore circumvents the limitations associated with conventional tissue culture. Although the TIB system requires the interplay of plant physiology and the chemical and physical sciences, growth rate is significantly enhanced therein since gas exchange is guaranteed (Watt 2012).

IITA’s TIB system is a “twin flask” type (Adelberg and Simpson 2002), having 1 container for the medium and the other for the cultures. It has potentials for both plantlet and yam microtuber production which will facilitate the production of quality breeders’ seed yam from which healthy foundation and certified seed yam will be multiplied. IITA’s TIB is established with 128 units and, when running at full capacity, can produce at least 12,000 seed yam in 1 year. It is programmable and remotely controlled online. It can also be used to fast-track genetic improvement through accelerated in-vitro variations and selection. Seed yam from this technology will be bulked in IITA’s aeroponics facility; other end-users include researchers, farmers, and public/private seed companies.

References

Adelberg, J.W. and E.P. Simpson. 2002. Intermittent Immersion Vessel Apparatus and Process for Plant Propagation. Internl. S/N: PCT/US01/06586.

Cabrera, M., R. Gómez, E. Espinosa, J. López, V. Medero, M. Basail and A. Santos. 2011. Yam (Dioscorea alata L.) microtuber formation in Temporary Immersion System as planting material. Biotecnologia Apl. 28: 4.

Watt, M.P. 2012. The status of temporary immersion system (TIS) technology for plant micropropagation.African Journal of Biotechnology 11: 14025-14035.

 

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