Abstract:
Cacao is a perennial tree crop
from the Malvaceae family. It is made up of
twenty-one species, with Theobroma cacao
as the commonest and one of the most
economically important crops globally. West
Africa is the largest region of producers. Lack
of availability of planting materials all year
round has been a major factor besetting cocoa
production in West Africa and has led to a
drastic reduction in production in the last
decade. Establishing an efficient in vitro
protocol for germinating zygotic embryos of
local West African cocoa varieties offers a
solution to expedite large-scale planting
material production to enhance cocoa
sustainable production and material
availability. An effective in vitro protocol for
germinating zygotic embryos of local West
African cocoa varieties will help produce
large planting materials within the shortest
possible time and promote sustainable supply,
which could boost cocoa production within
the region and increase the availability of
planting materials. Four West African local
varieties of Theobroma cacao were cultured
in three explant types on both Driver and
Kuniyaki Walnut (DKW) basal salts and
Murashige and Skoog (MS) culture media
without growth regulators for twenty days.
The three explant types included seeds with
mucilage (SWM), seeds without mucilage
(SWtM) and embryo axis (EA). The cultured
explants were kept in a growth room of light
intensity with a temperature of 25 ℃ ±1,
relative humidity of 85% and the three
explant types responded differently.
Germination responses significantly varied
among the explant types. SWtM sprouted
earlier with more than 160 plantlets before
day 5, followed by EA with 150 plantlets
before day 5, while SWM showed the lowest
mean germination percentage of 8%
compared to SWtM and EA with 9% Early
sprouting was observed in the DKW medium
with almost 250 (34.72%) plantlets
development before day five compared to the
MS medium with less than 150 (20.83%)
plantlets development, but the MS medium
produces the optimal growth performance
with the best mean germination time of 0.08
per day, final germination percentage of
71.39%, and development of the growth
parameters leading to the development of
plantlets, including 2.60 for number of leaves.
This study shows that the media for in vitro
culture and the source of explants
significantly influence seed germination and
produce dissimilar effects on the germination
of zygotic embryos of Theobroma cacao
varieties. The study recommends using
SWtM on DKW medium for early sprouting
of seeds of Theobroma cacao followed by a
transfer into MS medium for seedling
development into plants.
