Endogenous Auxin on Adventitious Embryo Formation from Calli of Sweet Orange and Satsuma Mandarin

Abstract

The calli of sweet orange and satsuma mandarin were cultured in a liquid medium and separated through meshes of φ0.5 mm, 1.0 mm, and 2.0 mm. The calli were separated again by the concentration gradient at 40% and 50% Percoll. The calli were cultured on the medium for embryogenesis, the implication of endogenous auxin was analyzed upon embryo formation. Adventitious embryos readily formed from the callus φ1.0 mm-40% in 'Valencia' orange and φ1.0 mm-50% in 'Yoshida' navel orange. In satsuma mandarin 'Miyagawa wase' and 'Sugiyama unshu', the callus of φ1.0 mm-40% formed relatively high number of embryos, which was still 1/8 to 1/15th that of sweet orange. The endogenous auxin content in callus decreased after the embryo formation, whereas it remained relatively high in callus which did not undergo embryogenesis. The results suggest that the decrease in auxin contents is related to the embryo formation.