Reconsidering how to dry orthodox seeds for improved ex situ conservation outcomes

Societal Impact Statement Ex situ seed conservation is an essential tool in our efforts to conserve wild and cultivated plant diversity, as mentioned in the Global Strategy for Plant Conservation and the Sustainable Development Goals. While there are established standards which seed banks follow, it is important that we continue to evaluate protocols and optimize processes. Here, we encourage seed banks to re‐evaluate their seed drying protocols. There is increasing evidence that two‐stage drying, an initial active drying phase followed by equilibrium drying to the target moisture content for storage, increases the subsequent longevity of seeds which will result in improved conservation outcomes. Summary Billions of seeds are stored around the world in seed banks—either conservation seed banks preserving species diversity or genebanks conserving primarily intra‐species agrobiodiversity. As well as providing long‐term conservation, many of these seed banks offer samples of seeds for use in restoration programs, breeding and other research activities. Most seed banks follow international standards to manage collections, with specific standards concerning each step in the conservation cycle. One of the standards describes the conditions under which seeds should be dried before packing and storage: Seeds should be dried to equilibrium in a controlled environment of 5°C–20°C and 10%–25% relative humidity. These conditions theoretically mean that seeds will be close to an optimum moisture content for the maintenance of viability during storage. However, considerable gains in subsequent longevity can potentially be achieved, particularly for seeds that are harvested before maturation drying is completed in planta, if a two‐stage drying process is adopted. The first, brief active drying phase should be at 30°C–45°C and 20%–70% RH and should be followed by slower final drying towards equilibrium in a cool, dry environment (15°C ± 5°C with 15% ± 5% RH). We encourage seed banks to consider this two‐stage drying approach, even before the genebank standards are revised. Conservation research is important for improving current best practices to ensure the effective safeguarding of species and agricultural biodiversity.