Two-step drying of soya bean seed germplasm often improves subsequent storage longevity

Abstract It is recommended that seeds for genebank storage are dried to low moisture content at 10–25 °C, 10–15% RH, but in some crops, an initial warmer drying temperature may provide better longevity. Seeds of diverse accessions of soyabean ( Glycine max (L.) Merr.) produced in three seasons and harvested shortly before or at harvest maturity were initially dried at 17, 30 or 40 °C with 15% RH and subsequently at 17 °C with 15% RH; seeds were fumigated either before or after initial drying. Seed longevity in hermetic storage at 45 °C with approximately 9% moisture content was affected by the initial drying treatments, but effects varied among treatment combinations and accessions. Seeds harvested before harvest maturity, at 10–14% moisture content, tended to benefit from warmer temperature drying. Fumigation before initial drying resulted in shorter longevity than fumigation afterwards for about 70% of harvested seed lots. Most treatment combinations across all experiments showed seed longevity was improved, often considerably, by 4 days’ initial drying at 40 °C compared to drying at 17 °C throughout. Longevity was also improved in many treatment combinations (fewer than at 40 °C) by initial drying at 30 °C compared to 17 °C. In a minority of treatment combinations, seed longevity was reduced by drying at 40 or 30 °C compared to 17 °C. The research shows a potential benefit to subsequent seed longevity from initially drying soya bean seeds at 40 °C, rather than 10–25 °C, for most accessions, particularly those harvested early; this benefit may have been due to greater post-harvest maturation in the warmest regime.