Metabolic Dysfunctions and Dynamic of Antioxidant Enzymes Activity in Developing Recalcitrant Cacao (Theobroma cacao) Seeds at Different Storage Conditions

A potential breakthrough in improving the short-term preservation of recalcitrant cacao (Theobroma cacao) seeds is the specific conditions with slow-drying procedures. Thus, this study aimed to elucidate the effect of storage conditions on the physio-chemical and reactive oxygen species (ROS) antioxidant enzymes with slow-drying processes in cacao seeds. Seeds from ripened cacao pods (clone PBC 123) were demucilaged, placed in a zip-lock polyethene bag, and stored at 14°C and 16°C (40% and 80% relative humidity [RH]), room temperature (RT; 25°C), and control (0 days of storage). Seeds at 14°C tend to retain the highest respiration rate during 12 days of storage. Their impaired respiratory activity is reflected through the highest accumulation of soluble sugar during the first 6 days after storage, lower protein content with the highest antioxidant enzyme activities, indicating increased ROS production. Antioxidant enzymes involved in the glutathione-ascorbate cycle, ascorbate peroxidase, and glutathione reductase activity were crucially responsive to the oxidative status within seed cells at 14°C. In contrast, seeds demonstrated decreasing moisture content during storage (RT and 16°C, 40% RH). They displayed higher ROS (hydrogen peroxide) signalling but within the oxidative concentration threshold, giving the advantage of holding seeds with lesser exposure to oxidative stress. As the condition of 16oC, 40% RH produced lesser germinated seeds (8% to 12%) than seeds at RT during storage, it is then suggested to be the alternative to minimise seed’s physio-chemical changes, contributing to the maximum germination characteristics for 12 days of storage, and thus, increase the potential for further exploration.