Genebank management is a field in its own right; it is multifaceted, requiring a diverse set of skills and knowledge. Seed physiology is one area that is critical to the successful operation of seed genebanks, requiring understanding of seed quality during development and maturation, seed dormancy and germination, and seed longevity in storage of the target species. Careful management of the workflow between these activities, as seeds move from harvest to storage, and the recording and management of all relevant associated data, is key to ensuring the effective conservation of plant genetic resources. This review will discuss various aspects of seed physiology that genebank managers should be aware of, to ensure appropriate decisions are made about the handling and management of their seed collections.

To maximize seed longevity, seeds should be harvested at optimal maturity, that is, when seeds have acquired maximum physiological quality before deterioration begins. The aim of this study was to map the variation in temporal patterns of lentil (Lens culinaris Medik.) seed quality development when grown across four regeneration environments, which differ in the level of temperature and humidity control throughout the growing season, at the Australian Grains Genebank. Seeds of two lentil accessions (76080 and 76072) were harvested at different stages throughout development, commencing at 21 d after 50% anthesis until a maximum of 130 d. At each harvest, physiological quality traits, including germinability (fresh and dried seeds) and seed longevity, were determined, as well as seed dry weight and moisture content. Seeds of both accessions, and in all environments, started to accumulate physiological quality early on in development but did not reach their maximum until 3–54 d after mass maturity. The temporal patterns of desiccation tolerance and storage longevity were highly influenced by the environmental conditions during the maturation drying phase, affecting both ‘when’ maximum quality was attained and for how long it was maintained, thereafter. Seeds did not show a typical developmental response, rather variation was observed in seed quality development both between and within accessions grown in the different environments. The poorest storage longevity was seen when seeds of both accessions were grown in the cooler, temperature-controlled glasshouse, and the maximum longevity was observed in the warmer, semi-protected environments of the green and the big igloo for accessions 76080 and 76072, respectively.

Orthodox seed longevity systematically increases with reduction in temperature and moisture content, as described by the Ellis and Roberts viability equations. These equations have species-specific parameters which quantify the inherent longevity of seeds of a particular species and their sensitivity to change in moisture content. This research investigated the effect of moisture content on lentil ( Lens culinaris) seed longevity during experimental storage. Seeds of an elite breeding line were stored under hermetic conditions at six different moisture contents (7.6, 8.1, 8.8, 10.1, 11.5, 12.6%) at 60°C. Ability to germinate was determined at scheduled intervals, and longevity (σ) was estimated for each treatment. The values of the constants K_E (8.0008) and C_W (3.746) were estimated using linear regression, by plotting log σ against log moisture content, combined with the universal temperature constants (C_H = 0.0329, C_Q = 0.000478). The application of these moisture constants (K_E and C_W) was tested by comparing the predicted viability loss of two lentil accessions with their observed longevity under hermetic storage at 12.0% moisture content and 45°C. The validity of these constants for predicting lentil seed longevity was proven, with an R² = 0.912 (P < 0.001).

Seed (gene)banking is an effective way to conserve cultivated and wild plant diversity. However, long-term funding is not always consistently sufficient, and there is a need to both strengthen the effectiveness of genebank operations and maximize cost efficiency. One way to control the cost of maintaining a germplasm collection is to optimize the quantity of seeds per accession that is placed into storage, depending on the expected length of time a seed lot will remain above the viability threshold, expected rates of use for distribution and viability testing and on the requirement to ensure a reserve. Here, we express this as an equation, which can be applied to cultivated species and adjusted to different scenarios, but also to inform decisions about use of accessions of wild species where the number of seeds available is limited, a common scenario for wild-species conservation seed banks. For many crop genebanks, given the expected longevity of seeds, it would be worthwhile to increase the number of seeds produced and processed for storage. This would also help to diminish the risk of genetic drift due to frequent cycles of regeneration but would have implications in terms of how accessions are regenerated, in particular, how many plants are used for regeneration and the size of storage facilities. The equation we present can also be rearranged and used to plan how to allocate seeds for testing and use when the number of seeds available is limited. This may have particular relevance for species conservation seed banks.

The Genebank Standards for Plant Genetic Resources recommend that genebanks periodically monitor the change in viability of their stored germplasm to ensure timely regeneration. The Australian Grains Genebank (AGG) has been recording germination data on orthodox seeds from tropical grain crops, stored under long-term storage (−20°C), for 40 years. Real-time viability data, collated from germination tests carried out on seedlots which had been in storage for a minimum of 20 years, from six agriculturally important grain crops ( Sorghum bicolor, Phaseolus vulgaris, Glycine max, Vigna radiata, Cajanus cajan and Vigna angularis ) was analysed by probit analysis. For each species independently, a common loss in viability was observed for all seedlots showing a consistent decline in viability during storage; with observed longevity estimates (σ; time for viability to fall by 1 NED/probit) of 17.4, 30.7, 33.2 49.6, 48.8, 63.5 and years for Vigna angularis, Cajanus cajan, Phaseolus vulgaris, Glycine max, Sorghum bicolor , and Vigna radiata , respectively. Common values of σ were subsequently used to determine species-specific viability monitoring intervals, based on the results of the last germination test. Dynamic monitoring intervals are a cost-efficient strategy that will avoid the over-use of seed through too frequent viability monitoring whilst still ensuring the timely regeneration of material. With funding shortfalls often reported as the main contributing factor to regeneration and viability testing backlogs, the ability for genebanks to maximise cost-efficiencies, where possible, is paramount to secure the genetic integrity of stored germplasm; particularly as collections continue to grow.