Family : Sterculiaceae
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Common names: Sp: cacao; Po: cacau; En: cocoa; Fr:
cacao; the tree is called cacaoyer. The Latin name comes from the Greek
theos (God) and broma (beverage).
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Origin and Geographical Distribution: Humid forests
of tropical South America. Now pan tropical.
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Uses |
The seeds are processed into cocoa powder and cocoa butter, used mainly
to make chocolate; the pulp is eaten fresh or made into juice and sherbets.
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Explants |
Collect the explants from high yielding well grown mature trees.
Use tender leaves, shoots, nodal cuttings and zygotic embryos as
explants.
Use flower buds showing pollen tetrad stage of anthers, and flat
beans from mature pods for haploid studies.
Carefully bring the explants materials to the lab in polythene bags
to avoid sudden wilting.
Cut pieces of tender shoots kept in a mixture of 0.01% HgCl2 with
Bavistin for 15 min under UV light. This same method is applicable
for young leaves, flower buds and flat beans (Zygotic embryos).
After treatment wash the explants in double distilled water.
Explants should be treated in ascorbic acid + citric acid solution
(100 ppm) to prevent browning.
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Media
and Culture conditions |
Prepare various media with various hormone concentration
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a) Callus induction medium for Cotyledon
explants (mg/l)
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MS + 0.5 NAA + 0.5 BAP + Sugar 30 g + Coconut water 15%MS + 0.5 NAA + 0.6 BAP + Sugar 30 g + Coconut water 15%
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b) Callus induction medium for stem explants
(mg/l)
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MS + 0.5 NAA + 0.5 BAP + Sugar 30 g + Coconut water 15%MS + 1.0 NAA + 0.1 BAP + 1.0 2,4-D + Sugar 30 g + Coconut water
15%
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c) Callus induction medium for leaf explants
(mg/l)
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MS + 0.5 NAA + 0.5 BAP + Sugar 30 g + Coconut water 15%MS + 1.0 NAA + 1.0 BAP + Sugar 30 g + Coconut water 15%
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Inoculate the explants into culture tubes containing above media.Cultures should be maintained in adjusted temperature at 26oC ± 2oC.The photoperiod maintained at 16 hrs light and 8 hrs darkness.Sub-culturing should be done periodically after 2 to 3 weeks intervals
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In
vitro response |
Observe the different explants and its response in various medium supplemented with
various hormones.
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Response
of Cotyledon tissues: |
Observe callus initiation in 10-15days after inoculation.
Record embryogenesis on MS medium supplemented with low levels of
NAA (0.5 mg/l) + BAP (0.5 mg/l).
Notice rhizogenesis when NAA (10.0 mg/l) higher level + BAP (0.1
mg/l) in low level.
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Response
of tender leaf tissues: |
Observe the leaf callus on MS medium supplemented with NAA (0.1 mg/l)
,BAP (0.5 mg/l), 2iP (5.0 mg/l), adinine sulphate (80 mg/l) and casein
hydrolysate (500 mg/l)
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Response
of tender shoots: |
After 7-10 days, observe maximum growth of callus on MS medium supplemented
with NAA (1 mg/l) , BAP (0.10mg/l) and 2,4-D (1.0 mg/l).
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Response
of anther culture: |
Maintain the culture in Nitsch (1969), Gamborg's B-5 (1975).on B-5
medium with NAA (1.0 mg/l) + BAP (0.5 mg/l)
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Practical
Utility |
Anther culture would help the production of haploid and homozygous
lines for developing new hybrids. This protocol could used for screening
against certain diseases caused by fungal, bacterial pathotoxins.
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IBA: Indole-3-butyric
acid; 2,4-D: 2,4-dichlorophenoxyacetic acid; NAA: a-naphthaleneacetic
acid; MS basal medium-Murashige and Skoog (1962); 2-iP: 6-y-y-dimethylallylamino
purine; Ads: Adenine sulphate
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