Lipid Thermal Fingerprints of Long-term Stored Seeds of Brassicaceae

Mira Mira,González-Benito González-Benito,Liu Liu,Nadarajan Nadarajan,Pritchard Pritchard

doi:10.3390/plants8100414

Mira Mira, González-Benito González-Benito + Show 3 more

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https://doi.org/10.3390/plants8100414

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Abstract

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.

Highlights

Optimal conditions of humidity and temperature for the long-term storage of seeds are still the subject of debate, principally as there are few long-term data sets
Seeds of two species from Royal Botanic Gardens Kew (RBG Kew), Alliaria petiolata and Lesquerella gordonii showed a drastic decline in germination following storage for 32 and 8 years from c
Lipid phase transitions were detected in differential scanning calorimetry (DSC) scans of dry seeds of all species, and the scans were consistent with published evidence on Brassicaceae species generally producing oily seeds

Summary

Introduction

Optimal conditions of humidity and temperature for the long-term storage of seeds are still the subject of debate, principally as there are few long-term data sets. Seeds that tolerate further drying may benefit with improved longevity, the minimum safe humidity for long-term storage appears to vary with species, and possibly with seed lot. Equilibrium relative humidity (equivalent to about 2.5–6.5% moisture content, depending on seed oil content) and subsequent storage at −20 ◦ C has been shown to be safe [1]. Relative humidity, RH) may not store well at −20 ◦ C. relative humidity, RH) may not store well at −20 ◦ C These latter seeds, oft-called “intermediate”, tend to lose germinability quite rapidly at cool (5 ◦ C) or cold (−20 ◦ C) storage temperatures, for example, within 1 year [5]. It is possible that such seeds could initially respond to drying as if an Plants 2019, 8, 414; doi:10.3390/plants8100414 www.mdpi.com/journal/plants

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