OPTIMIZING SEED DRYING PERIODS FOR MOISTURE REDUCTION IN SELECTED CROP SPECIES FOR LONG-TERM CONSERVATION

Abstract

Maintaining the low seed moisture content is essential for extending seed longevity in gene banks. The conserved seeds at the National Genebank in Sri Lanka must be reduced to 5% before long-term storage in accordance with international standards. This study aimed to determine the optimal drying period to achieve the 5% moisture level of several selected crop species. The research was conducted at the Seed Conservation Unit of the Plant Genetic Resources Centre (PGRC), using four traditional rice (Oryza sativa) varieties (Dik Wee, Kuruluthuda, Masuran, Sudu Heenati), foxtail millet (Setaria italica), proso millet (Panicum miliaceum), groundnut (Arachis hypogaea), common bean (Phaseolus vulgaris), mustard (Brassica nigra), and sesame (Sesamum indicum). The initial seed moisture content of all species was measured before drying. Seeds were first transferred to a drying room (16°C, 25% RH) to reach approximately 7% moisture content and then placed in a drying cabinet (17°C, 20% RH) to achieve 5% moisture content. Subsequently, seeds were stored under medium-term storage conditions (5°C, 25% RH) to verify their readiness for conservation. Germination, viability, and vigor assessments were conducted throughout the drying and storage phases. Tested seeds exhibited a rapid decline in moisture content to 7%, followed by a slower reduction to 5%. Drying behaviors were highly variable among crop species, in both drying phases. Qualitative aspects of seeds; germination, viability and seedling vigor, remained stable throughout the drying and storage period, while common beans illustrated a rapid loss of germination. Results indicated that reducing the moisture content to 5% was effective for the long-term conservation of studied species. The identified drying periods can be effectively applied to reduce moisture to 5% in future conservation efforts at the National Genebank of Sri Lanka.