HIGHLY-EFFICIENT SOMATIC EMBRYOGENESIS FROM CELL SUSPENSION CULTURES OF PHALAENOPSIS ORCHIDS BY ADJUSTING CARBOHYDRATE SOURCES

The influences of various carbohydrate sources, dried yeast (DY), and 6-benzylaminopurine (BA) were estimated on growth and development of shoot tip-derived suspension cells of phalaenopsis orchid. Among the carbohydrates tested on Doriataenopsis cultured on gelled medium, glucose at 58.4 mM gave the highest efficiency of protocorm-like body (PLB) formation. Maltose and sorbitol only induced PLB formation without callus proliferation. Sucrose induced comparable callus proliferation to glucose but without PLB formation. In contrast, fructose resulted in half the amount of callus proliferation as occurred with glucose. Lactose was an inadequate carbon source as neither PLB formation nor callus proliferation occurred. DY enhanced cell proliferation at 0.1–1 g l21 but inhibited both cell proliferation and PLB formation at 10 g l21. Low BA (0.4mM) slightly increased callus proliferation but inhibited PLB formation. Only one treatment, sucrose and 1 g l21 DY, yielded a small number of plants. For suspension cultures of Phalaenopsis Snow Parade and P. Wedding Promenade, PLB formation was most efficiently induced by sucrose at 29.2 mM for P. Snow Parade and 14.6 mM glucose for P. Wedding Promenade. Histological observation revealed that cells in suspension culture developed into plants through the same developmental process as germinating seeds. Key words: PLB formation; embryogenesis; micropropagation; sugar; Doritaenopsis; orchid