A presentation by Eshan Dulloo at the European Plant Genetic Resources Conference 2011. The conference brought together global particpants interested in making greater use of the agricultural biodiversity conserved in genebanks.
48. Studies have shown that lowering storage temperature increases the critical moisture level, which suggest dangers of overdrying seeds if we dry at lower RH
49. Various RH-temperature combinations for a given species. Important for genebank curators to clearly understand relationship to decide on best drying conditions.
50.
51. Preferred: - 18°C or cooler with 3-7% seed moisture content (depending upon species).
52. Use of any type of sealed moisture-proof containers
56. Viability monitoring test set at 1/3 of time predicted fro viability to fall to 85% of initial viability
57. Germination should exceed 85% for most cereals & 75 % some vegetables and lower for some wild or forest species
58. Carried out at (or soon after) receipt and subsequently at intervals during storage.
59. Initial germination test should be carried out on a minimum of 200 seeds drawn at random from the accession
60.
61. The sample size of the accession to-be-regenerated contains a minimum number of plants which capture at least 95 percent of alleles with a minimum frequency of 0.05
65. It is desirable to use 100 plants or more for regeneration to avoid the probability of large losses of alleles.
66.
67. Passport data of 100 percent of the accessions are documented, maintained in suitably designed databases and duplicate set maintained outside genebank
90. For many standards there is still lack of evidence – more research required
91.
Editor's Notes
In order to add value to collections, it was felt important to suggest new standards for characterization.
Research after 1994 have shown that maximum longevity is achieved at a critical MC below which there is no gain. Drying conditions that achieve the critical moisture level at the storage temperature should be determined using water sorption isotherms which show the relationship between the amount of water in the seeds, usually expressed as a percentage of the total seed weight, and their RH. There could be different combinations of relative humidity and drying temperature for given species. Isotherm relationships, predicted based on seed oil content, are available online at the Kew Seed Information Database (SID) website (see references). Genebank operators should clearly understand the relationship between relative humidity and storage temperature to be able to decide about the best combination for their seed drying environment.