Evaluation of onion (Allium cepa L.) seed after 10 years of storage at 5, -18, and -196 degrees C.
1995
Stanwood P.C. | Sowa S.
Long-term storage strategies for seed germplasm are needed to assure preservation of diminishing plant genetic resources. Cryopreservation in liquid nitrogen (-196 degrees C) is being studied as a potential method to reduce the rate of seed deterioration and thus increase the storage life of the seed. Onion (Alliun cepa L.) seed was stored for 10 yr at 5, -18, and -196 degrees C (liquid nitrogen) and evaluated for germination, seedling root length, electrolyte leakage, and O2 uptake to determine long-term storage response. Average germination of seed stored d -18 and -196 degrees C did not decline over the 10 yr period, while germination of seed stored d 5 degrees C dropped from 94 to 68%. Variation in moisture content was observed in seed stored at 5 and -18 degrees C, with no variation noted at the -196 degrees C-storage temperature. The variation in moisture content may have influenced seed deterioration at the 5 degrees C-storage temperature. It is less likely that the variation in seed moisture content was a contributing factor at the -18 degrees C-storage temperature. Electrolyte leakage results, an indication of seed membrane integrity, were inconclusive. Average seedling root lengths of 2.8, 5.7, and 6.6 mm and seedling O2 uptake rates of 124, 156, and 176 pmol mg-1 min-1 (5, -18, and -196 degrees C storage, respectively) were observed, suggesting less physiological deterioration at the -196 degrees C storage temperature. Based on seedling root length, O2 uptake rates, maintenance of seed moisture content and seed germination, it was concluded that seed deterioration was greater at 5 > - 18 > -196 degrees C. Maintenance of seed germplasm at 5 degrees C in this experiment was not satisfactory. Liquid nitrogen and -18 degrees C storage for up to 10 yr was acceptable. Cryopreservation of seed germplasm appeared to result in superior seed vigor compared with the -18 degrees C storage.
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