Culture of Immature Embryos of Coconut, Cocos nucifera L: Callus Proliferation and Somatic Embryogenesis

Abstract

The culture of immature embryos of coconut (Cocos nucifera L var. typica) was attempted
with a view to developing a technique for clonal propagation. Embryos, 6-7 months
postanthesis produced whitish, compact, embryogenic callus tissues in the presence of 12-20
uM 2,4-D. Callus was maintained by subculture on a medium of the same composition.
About 50% of the callus cultures produced globular embryos when transferred to 8 pM 2,4-D.
Embryos in 22% of these cultures germinated and produced shoots, 6 mm long, when 6-
benzylamino purine and kinetin (10 p.M each) were incorporated into the culture medium.
The age of the embryo was an important factor determining callus proliferation and
subsequent embryogenesis. More than 50% of embryos excised from 6-7-month-old nuts
produced embryogenic callus tissues. Five to six-month-old nuts were not mature enough for
excising the embryos. Embryos from older nuts (8 months and above) germinated in culture.
Only a small portion of the immature embryo produced embryogenic callus tissues. The
future root region proliferated into a brownish callus which in turn produced roots profusely.
The cotyledon of the immature embryo expanded and developed into a haustorium without
any sign of callus formation. The shoot apex produced a few plumular leaves but no callusing
was observed.