Somatic Embryogenesis in Three Magnolia Species

Abstract

Cultures were initiated from immature seeds of three species of magnolia: sweetbay magnolia (Magnolia virginiana L.), fraser magnolia (M. fraseri Walt.) and yellow cucumbertree [M. acuminata var. cordata (Michx.) Sarg.]. Immature seeds were bisected longitudinally and cultured on a solidified conditioning medium containing 2 mg 2,4-D/liter, 0.25 mg BA/liter, 40 g sucrose/liter, and 1 g casein hydrolysate/liter. Cultures were maintained in the dark at 22C and transferred to fresh medium at monthly intervals. Within 2 months of culture, somatic embryos or proembryogenic masses proliferated from one end of the endosperm mass. Somatic embryos and proembryogenic masses of each species were cultured on a hormone-free version of the conditioning medium to complete maturation and then transferred to the same hormone-free medium, minus casein hydrolysate, to initiate germination. Germinants were transferred to a hormone-free plantlet development medium for conversion. Plantlets of all three species survived transfer to soil mix and continued to grow. Chemical names used: (2,4 -dichlorophenoxy) acetic acid (2,4-D), N- (phenylmethyl)-1H-purin-6-amine (BA).