Effect of Embryogenic Callus Conditions on Plant Regeneration in Satsuma Mandarin (Citrus unshiu Marc.)

The ability to form embryiod from callus in satsuma mandarin is low and unstable. In this study, the conditions of embryogenic calli induced from nucellar tissue for promotion of plant regeneration in satsuma mandarin were investigated. The calli of I, II and III line were divided into two sizes of 0.5 mm and 1.0 mm in diameter and two weight gradients of percoll at 40% and 50% though the filter mesh. The frequency of embryo formation from $\phi$ 1.0mm-40% was slightly higher than callus that from others. Adventitious embryoids developed to a globular stage were transferred to regeneration medium. In 'Miyagawa Wase', the embryos from I and II line developed into a heart stage from most of $\phi$ 0.5 mm- 40% and $\phi$1.0 mm-40% calli, but it failed in 'Sugiyama Unshu'. In the cultivar of 'Miyagawa Wase', 63% of adventitious embryos transferred to the regeneration medium developed into the heart stage from the most $\phi$ 1.0 mm-40% calli of I line, but of 'Sugiyama Unshu' failed in some calli condition. The embryoids from two callus lines developed further to shoots and plantlets, while the embriods from III line abnormal failed to regenerate in the cultivar. From these results, it is suggested that the plant regeneration from embryogenic callus in satsuma mandarin could be affected by callus conditions.