Survival of dry and ultra-dry seeds of carrot, groundnut, lettuce, oilseed rape, and onion during five years' hermetic storage at low temperatures.
1996
Ellis R.H. | Hong T.D. | Astley D. | Pinnegar A.E. | Kraak H.L.
Since 1974 the advice for genetic resources conservation by long-term seed storage has been to store seeds dry at 5+-1 % moisture content at a temperature of -18 deg C or less. Investigations were carried out to determine whether or not hermetic storage at lower moisture contents (those in equilibrium with about 10 % r.h. at 20 deg C) would provide better seed survival, particularly in circumstances where refrigeration cannot be provided. Seeds of carrot, groundnut, lettuce, oilseed rape, and onion were stored hermetically for five years in four environments (dry or ultra-dry seed storage moisture contents combined factorially with temperatures of 20 deg C or -20 deg C), replicated at two or three sites, and viability (assessed by ability to germinate normally in standard germination tests) estimated at six-monthly intervals. No loss in seed viability was detected during this period in any of these species at -20 deg C with either moisture content. Significant loss in viability occurred at 20 deg C, however, and was more rapid in dry (5.5-6.8 % moisture content) than ultra-dry (2.0-3.7 % moisture content) seeds. The results of this five-year study at each of the three sites confirm that storage at -20 deg C rather than 20 deg C is beneficial to seed survival, and that hermetic storage at 20 deg C of seeds first dried at 20 deg C to moisture contents in equilibrium with about 10 % r.h. provides greater longevity than 5.5-6.8 % moisture content in these five species.
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