MSc

The research work entitled “Enhancement of storage life of synthetic seeds of cocoa
(Theobroma cacao L.) through germination inhibition, desiccation and low temperature
treatments” was carried out at Plant Tissue Culture Laboratory, College of Forestry,
Vellanikkara, during the period 2012-2014. The objectives of the research work were to
enhance the longevity of synthetic cocoa seeds through the application of different
concentrations of chemical inhibitors/osmotica, desiccation at different RH for varying
durations and low temperature treatment under refrigerated conditions and hence to prepare
a storage protocol for synthetic cocoa seed. Synthetic seeds using calcium alginate
encapsulation technique were prepared from embryonic axes of cocoa containing ¼
cotyledon. The experiments revealed that, presence of different chemical inhibitors in
storage medium significantly influenced radicle emergence of synthetic seeds of cocoa. ABA
at 10
-3
M and 10
-4
M level did not inhibit the radicle emergence of synthetic cocoa seeds and
seed mortality were observed by 20
th
and 25
th
day respectively in both the concentrations.
All synthetic seeds stored in higher concentrations of coumarin (10
-2
M) and CCC (1 M)
containing ½ MS basal medium were found mortal on 10
th
and 15
th
day respectively. The
presence of lower levels of coumarin (10
-3
M) or CCC (10
-1
M) in the storage medium helped
to extend the longevity of synthetic cocoa seeds for 60 days without complete loss of viability.
The combination of 10
-3
M coumarin and 10
-1
M CCC in the storage medium extended the
longevity of the cultures for 67 days. Low levels of osmotica in the storage medium (100
mM sorbitol and 5% PEG) did not inhibit the germination of synthetic cocoa seeds whereas,
higher levels (500 mM sorbitol and 15% PEG) had a negative influence on the cultures.
Among the different osmotic treatments, 250 mM sorbitol fortified medium was found to be
best as it could arrest radicle emergence in 42.97 % cultures. Longevity of more than 40
days were observed for synthetic seeds subjected to desiccation treatment: 85.3% RH (36
hours), 78.6% RH (24 hours and 36 hours) and 46.6% RH (18 hours and 24 hours). A
longevity of only 15 days were obtained for synthetic seeds subjected to low temperature
treatment in refrigerated conditions at 4ºC. The synthetic seeds stored in 10
M CCC and
10
-3
M coumarin added storage medium, when transferred to ½ MS basal medium after 60
days showed a maximum storage life of 98 days and 92 days respectively. The study was
able to enhance the storage life of synthetic cocoa seeds by 9 days compared to a previous
study by Shiran, (2012).
Based on the results of the experiments conducted, a protocol for short and medium
term storage of cocoa seed was developed.