Protocols for Micropropagation of Woody Trees and Fruits

IN VITRO MUTAGENESIS IN BANANA 549
Figure 3. In vitro regeneration of banana via somatic embryogenesis. A) Male inflorescences
collected from field grown plants, each about 25–30 cm in length. B) Male inflorescence,
aseptically reduced to 10 cm length. C) Immature male flower buds cultured on BM1 medium,
bar = 4 mm. D) Embryogenic callus with somatic embryos on the surface, bar = 4 mm. E)
Developing somatic embryos. F) Embryogenic Cell Suspension in BM2G medium. G)
Embryogenic cell clusters. H) Fully developed somatic embryo, bar = 5 mm. I) Somatic
embryo conversion on BM3 medium.
In the span of initial 12 weeks (induction phase), the cultures shall be examined for
the contamination and the morphogenetic response every alternate week. Thereafter
these shall be observed weekly for any embryogenic response from the inoculated
tissues. The explants curl up and show callus formation during initial 4 weeks.
Subsequently, most of the explants would turn black but still may exhibit some
meristematic globules on the surface. This is followed by the development of calli
consisting of individual embryos or compact callus formation (Figure 3D,E). The
compact callus is generally not suitable for initiating ECS. Good embryogenic
callus (EC) can be observed after 3–5 months of culture initiation, which can
subsequently be maintained on BM2G medium.
The conversion of the somatic embryos into plantlets (Figure 3H) can be
achieved on BM3 medium (approximately 1–2 monthly passages) followed by
transfer onto BM4 medium till fully grown plantlets with well developed shoot and
roots are obtained (4–6 weeks).