Rapid loss of seed viability under 4˚C gene bank storage

Gene banks aim to maintain seed viability as long as possible. How long seeds can be stored without substantial loss of viability is not well understood. Theory predicts that the viability of wheat and barley seeds is largely maintained for more than 100 years when stored at 4˚C. CGN stores its base collection at -20˚C, but for logistic reasons its active collection was maintained at 4˚C.

Users of CGN’s wheat collection reported a strongly reduced seed germination of CGN accessions. Therefore, germination tests were performed using wheat and barley seeds stored at 4˚C and -20˚C. Samples stored for 30 years at -20˚C had maintained their high initial germination of more than 90%, while at 4˚C the percentage germination had dropped to about 70%

Six years after these experiments part of the samples were retested. Seeds maintained at 4˚C showed a further reduction in germination, while an almost complete loss of germination was observed for several samples. In addition, the samples also showed a delayed germination, also pointing towards a reduced vitality.

The publication ‘Rapid loss of seed viability in ex situ conserved wheat and barley at 4°C as compared to -20°C storage’ was recently published online. Herein Rob van Treuren and co-authors emphasize the relevance of their findings. Firstly, the distribution of seeds with low viability is a bad service to users of gene bank materials. Secondly, gene bank curators that store also their base collection at 4°C should be cautious that no valuable genetic resources are lost.

In January 2018 CGN transferred all samples of the active collection to -20°C storage. Currently, CGN is working on the replacement of seeds that had been stored at 4°C for a relatively long period in order to ensure that users of CGN accessions can count on high-quality seed samples.