Dynamic dissolved oxygen concentration control for enhancing the formation rate of torpedo-stage embryos in carrot somatic embryo culture.

In utilizing somatic embryogenesis for transplant production, torpedo-stage embryos are harvested. In order to enhance the formation rate of torpedo-stage embryos to total embryos of all developmental stages in the culture at the time of harvest, a dynamic dissolved oxygen concentration (DO) control algorithm is proposed. The algorithm is based on the difference in developmental response of somatic embryogenesis to DO level depending on developmental stages, and the culture period was divided into three phases of different DO levels. The timing of the phase change was determined based on the formation rate of the embryos in each developmental stage in the suspension assessed by noninvasive monitoring of the culture. The induction of carrot (Daucus carroa L.) somatic embryogenesis resulted in doubled formation rate of torpedo-stage embryos by dynamic DO control compared to the 20% oxygen gas aeration, and 1.4 times higher formation rate compared to 6% oxygen gas aeration, while the total number of embryos did not differ among DO treatments. Plant conversion rate of torpedo-stage embryos cultured by the dynamic DO control was 70%, and was approximately the same as that in the control cultures. The relations between variations of medium pH and somatic embryogenesis were also analyzed.