Enhancement of storage life of cocoa (Theobroma cacao L) seeds through encapsulation and germination inhibition

Abstract

Studies on enhancement of storage life of cocoa (Theobroma cocoa L.) seeds through encapsulation and germination inhibition were carried out at the Department of Tree Physiology and Breeding , College of Forestry, Kerala Agricultural University, Vellanikkara, during 2010-12. 100-120 days old cocoa pods of, collected from polyclonal cocoa garden of Kerala Agricultural University were utilized for the standardization of microencapsulation techniques. To enhance longevity, germination inhibitor, osmoticum and desiccation were used and longevity of embryonic axes and synthetic seeds were observed. Cotyledon attachment on embryonic axis influenced the germination of embryo. The absence of cotyledon had checked the shoot regeneration of embryonic axes. Embryonic axes with ¼ cotyledon had good root and shoot regeneration with higher germination percentage. The storage medium influenced the longevity of embryonic axes. Higher longevity and viability was observed in ½ MS media while least longevity was observed in dry cotton. The presence of 10-3M coumarin in the basal media ( ½ MS) retarded the root growth of embryonic axes. ABA added to media in 10-4M concentration had increased the longevity of embryonic axes up to 56 days. Cycocel did not have influence on longevity of embryo. No combination effect by the germination inhibitor was seen in the experiment. Osmotic concentrations had positive influence on enhancing longevity of embryonic axes. Media with 250 mM sorbitol enhanced the longevity of embryonic axes to 65 days. Mannitol added media had crystallization during the storage which resulted in low longevity. Sodium chloride in higher concentration had checked the growth of embryonic axes and had shorter longevity. The encapsulation of embryonic axes had increased the longevity of seeds to 40 days while embryonic axes had longevity of 29 days. Maximum longevity of 70 days was observed in synthetic seeds stored in 250 mM sorbitol added media. Longevity was found less than 10 days in dry cotton due to absence of moisture content. The incorporation of MS media in the encapsulation, reduced the longevity of synthetic seeds. In addition, MS media and inhibitor combination in the encapsulation did not have influence on longevity. The MS media reduced the activity of inhibitor action. The 10-3M ABA, 250 mM sobritol and 500 mM sobritol in the encapsulation enhanced longevity to 65 days. Desiccation had a little effect on longevity and it had a negative correlation between RH level and longevity. Longevity had a positive correlation with duration of desiccation. The maximum longevity was possible by storing synthetic seeds in 250 mM sorbitol added media for 55 days and transferring to wet cotton for germination. It had a longevity of 89 days with 80 percent germination. The results of present study indicated that it is possible to store recalcitrant seeds by encapsulation and altering surrounding condition of embryo. The storage potential can be increased up to 3 months by the encapsulation and osmotic environment.