Evaluation of a new type of temporaryimmersion system (TIS) bioreactors for plantmicropropagation

Sammanfattning: Micropropagation has been revealed to be an efficient propagation method for production of large quantities of true to type and disease free plants, while traditional methods of micropropagation on solid medium are limited in commercial production due to high labor costs. Bioreactor production in liquid medium has therefore been studied and tested in recent years, but there are still no appropriate types of bioreactors until now. A new type of bioreactors based on the temporary immersion system (TIS) principle has been developed by Professor Margareta Welander at the Department of Plant Breeding and Biotechnology, the Swedish University of Agricultural Sciences (SLU), Alnarp, Sweden, and by Dr. AJ Sayegh, TC propagation Ltd, Bree, Enniscorthy, Co Wexford, Ireland. The aim of this study is to evaluate this new bioreactor for micropropagation using the three widely cultivated and important, horticultural species Digitalis lutea x purpurea, Echinacea purpurea ‘Magnus’ and Rubus idaeus ‘Mormorshallon’ in comparison with micropropagation on solid medium. Fresh and dry weights, the shoot production rate as well as survival and general plant appearance were evaluated. Further on, pH, conductivity, and composition of mineral nutrients and carbohydrates were measured regularly during the culture period. The acclimatization capability of the plantlets in greenhouse was also evaluated. The results show that this newly developed bioreactor is suitable for mass production of target plant species with a similar survival rate and plant quality to those from solid medium. The multiplication rate was either similar or better than that from solid medium. Plant analyses revealed a significant difference (p≤0.05) in fresh weight between TIS and the solid medium. However, the optimal cultivation medium differed between the species, where D. lutea x purpurea and E. purpurea ‘Magnus’ gained more weight with TIS while R. idaeus ‘Mormorshallon’ gained more weight with solid medium. No significant differences were found when comparing dry weights and the multiplication rate except for E. purpurea ‘Magnus’ where TIS resulted in a significantly p≤0.05) higher number of shoots of an adequate size for ex vitro acclimatization. Except for almost full depletion of iron and a 50% decrease in NH4+ concentration in the media of D. lutea x purpurea and E. purpurea ‘Magnus’, only minor changes in pH, conductivity,carbohydrate and mineral nutrient concentrations were observed over time for all species. Overall, the results of the medium analyses show that the bioreactor system is stable and reliable.