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.
