EFFECTS OF IN VITRO CULTURE METHODS DURING THE ROOTING STAGE AND LIGHT QUALITY DURING THE SEEDLING STAGE ON THE GROWTH OF HYDROPONIC EVERBEARING STRAWBERRY

To achieve the mass production of pharmaceutical proteins in genetically modified (GM) strawberry (Fragaria × ananassa Duch. cv. ‘HS138’), a continuous supply of a large number of uniform seedlings is required. We modified the micropropagation method which is suitable for subsequent hydroponic cultivation in a closed plant production system with artificial lighting. In this study, we conducted 6 treatments comprising 2 in vitro culture methods (PM: photomixotrophic culture or PA: photoautotrophic culture) during the rooting stage for 3 weeks and 3 light qualities (white, red and blue) for 4 weeks after transplanting to the ex vitro hydroponic system. The PM plantlets without roots were cultured on agar during the rooting stage, and their roots were washed to remove the agar before transplanting them to the hydroponic system. In contrast, the PA plantlets were cultured on a fibre rod as the supporting medium, which was the same medium as that used in the hydroponic stage. At the end of the rooting stage, the number of leaves, leaf area and dry matter were significantly higher in the PA plantlets than in the PM plantlets. During the hydroponic cultivation stage, the dry matter of seedlings was significantly higher under white and red light conditions than under blue light condition, irrespective of the culture method during the rooting stage. These results suggest that a combination of the PA culture methods during the rooting stage and white or red light condition after the transplanting can improve the efficiency of the propagation method used for GM strawberry production.