Vacuum storage and seed survival in pearl millet and sorghum

Sorghum (cv. Maldandi) seeds with 8.45% initial moisture content (MC) and 98% germination, and pearl millet (cv. Sadoré local) seeds with 9.2% initial MC and 94% germination were used for the study. The effect of vacuum on seed longevity was studied at three MCs: 6%, 10% and 14%. The MCs were adjusted by holding the seeds on saturated salt solutions of LiCl, MgCl and NaCl for about a week at 25°C. Each seed lot was then subdivided into aliquots of 5 g and hermetically sealed in aluminium foil envelopes containing air or vacuum packed at a pressure of -0.95 bar. Seeds were held at 50°C to accelerate ageing and sampled at regular intervals. The sampling intervals ranged from daily (14% MC) to 8 weeks (6% MC), depending on the storage treatment. In addition to those stored at 50°C some pearl millet seeds were also stored at 35°C. The initial viability of seeds was estimated at the beginning of storage and subsequently at each sampling point by conducting replicated germination tests on fifty seeds. Germination was expressed as the percentage of normal seedlings produced after seven days of incubation at 20°C. There was a gradual loss in germination rate under all storage conditions. Seeds stored under the higher temperature of (50°) and/or high MC (14%) deteriorated faster than with other treatments. Pearl millet seeds survived longer than sorghum under similar conditions of storage. Analysis of variance of the estimates of half-life for the viability of seeds showed significant effects of MC, vacuum packing and their interaction on seed survival at 50°C (P < 0.001). Seeds dried to 6% MC retained viability longer than those stored at 10% and 14% MC. Vacuum packing further enhanced seed longevity at 6% MC but not at 10 or 14% MC.