Germplasm conservation strategies ? impact of conditioning on the viability of dry pearl millet seeds

Seed deterioration is a continuous process andconservation of germplasm in ex-situ facilities necessitatestechniques that prolong seed longevity. A combination of3?7% seed moisture content (mc) and a storagetemperature below 0°C is suitable for long-termpreservation of orthodox seeds (FAO/IPGRI 1994).When seeds of different crops are dried to low moisturelevels, there is a decrease in weight and volume and whenlarge seeds dry too rapidly, the outside of the seed losesmoisture more rapidly than the inside of the seed and itreduces in volume more quickly leading to cracking ofthe seed coat (Ellis et al. 1985). Internal drying stressesalso increase susceptibility of seeds to mechanicalinjuries and the dryness of seeds is also critical to theoccurrence of imbibition injury (Ellis et al. 1990).Imbibition injury occurs in standard germination tests ofvery dry seeds, even when the germination medium is oflow osmotic potential. In addition to legume seeds,problems of imbibition injury have been encountered withforage legumes, cotton and sorghum (Sorghum vulgare)(Ellis et al. 1985). Imbibition injury to seeds depends onseveral factors such as seed maturation, age, mc andstorage temperature (Powell and Matthews 1979, Tully etal. 1981, Taylor and Prusinski 1990). Imbibition injury toseeds is a potential problem for genebanks handlinggermplasm samples of very dry seeds especially inmeeting the requirements for long-term storage. A criticalmc below which a constant proportion of seeds fail togerminate as a result of imbibition injury and thesusceptibility of very dry seeds to imbibition damage hasbeen reported by Ellis (1987) and Ellis et al. (1990)

D V S S R Sastry, H D Upadhyaya, C L L Gowda, 'Germplasm conservation strategies ? impact of conditioning on the viability of dry pearl millet seeds', Journal of SAT Agricultural Research, vol. 9, pp.4pp, International Crops Research Institute for the Semi-Arid Tropics, 2011