Thermal fingerprints for seeds of 20 crop wild relatives of Brassicaceae stored for 8 to 44 years at the Plant Germplasm Bank-Universidad Politécnica de Madrid and the Royal Botanic Gardens, Kew's Millennium Seed Bank-were generated using differential scanning calorimetry (DSC) and analyzed in relation to storage stability. Relatively poor storing oily seeds at -20 °C tended to have lipids with crystallization and melting transitions spread over a wide temperature range (c. 40 °C) that spanned the storage temperature, plus a melting end temperature of around 15 °C. We postulated that in dry storage, the variable longevity in Brassicaceae seeds could be associated with the presence of a metastable lipid phase at the temperature at which they are being stored. Consistent with that, when high-quality seed samples of various species were assessed after banking at -5 to -10 °C for c. 40 years, melting end temperatures were observed to be much lower (c. 0 to -30 °C) and multiple lipid phases did not occur at the storage temperature. We conclude that multiple features of the seed lipid thermal fingerprint could be used as biophysical markers to predict potential poor performance of oily seeds during long-term, decadal storage.
Keywords: conservation; crop wild relatives; differential scanning calorimetry (DSC), seed banking; longevity.