Maintenance of the genetic identity of accessions during genebank management is one of the cornerstones of genetic resources conservation. Accessions maintained in genebanks should remain as genetically similar to the original collected material as possible. It is very important to prevent the unintentional introgression of exotic genes, including transgenes, not already present in samples conserved in germplasm collections. Genebank processes are designed to avoid inadvertent introduction of genes through geneflow, avoid selection and retain genes in low frequencies within the population to ensure that maximum diversity is retained for future use. Best practices in genebanks should be able to achieve a high degree of probability that an accession maintains its original genetic identity over generations of regeneration and storage.
Genetic integrity can be at risk at all stages of the genebank handling process and careful handling procedures should be put in place to reduce the risk of loss of alleles or genes within the population or accession. These include paying attention to uneven loss of genotypes during storage by ensuring viability does not decline to low levels, using adequate sample size to capture genes in low frequencies for regeneration, providing isolation from pollen contamination and reducing the regeneration interval and carrying out regeneration in environments where the germplasm is well adapted to minimize selection and genetic drift during regeneration.
Even with careful handling, accessions may face genetic erosion or lose genetic integrity during long term storage over many cycles of regeneration. Routine testing schemes are required to monitor genetic identity and genetic erosion during genebank handling. In the past these tests have relied on checking morphological traits against standard lists of descriptors and comparing the traits in each generation to the original phenotype or population. New molecular tools have now provided the opportunity to monitor genetic integrity at the genotype level and laboratory tests are available to determine any unintentional genetic erosion or change in genetic identity.
This section provides information on the standards used to describe diversity and the methods used to detect changes in genotype, unintentional loss of alleles or genes or unintentional inclusion of genes and transgenes into accessions. Information is available on:
References and further reading
Hirano R, Jatoi SA, Kawase M, Kikuchi A, Watanabe N. 2009. Consequences of ex situ Conservation on the Genetic Integrity of Germplasm Held at Different Gene Banks: A Case Study of Bread Wheat Collected in Pakistan. Crop Science 49:2160-2166.