Regeneration

In Module 1, you learned that maintaining the genetic integrity of seeds is a core objective of genebanks. Many of the processes in subsequent modules are geared towards maintaining this genetic integrity. Whether by drying seeds to maximize their longevity or by cross-checking newly regenerated seeds against the seed file during cleaning, there are many ways a genebank can improve the quality of regenerated seeds. This make sure that the new generation of accessions are exactly the same, or at least as close as possible, to the original sample.

Genetic integrity can be threatened by pollen contamination, seed contamination, or unintended selection over many cycles of regeneration. Watch the video in which scientists talk about what measures they take to reduce genetic drift in regenerated seeds. As you watch, think about how every process tightly tied into the genebanks’ core mission of conserving diversity.

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Transcript: Video 3: seeds for the future

Narration:

When seeds lose viability, it’s time to regenerate. But regeneration brings some risks to genetic integrity. How can the genebank ensure that the new generation of seeds for storage contains exactly the same genes as the original accession?

Andres Godwin Sajise:

The genetic purity, or the genetic integrity of our collection is being ensured to the highest level. So for the seeds that we use for regeneration, the mother seed that we use should only come from the first, second, up to the third generation. So that’s the farthest we could go from the original seeds that we received in the collection, to ensure that there is no genetic drift or any change in the population.

Narration:

In IITA they’re regenerating Bambara groundnuts. With the right care, the young plants will grow and bear seeds to renew the viability of the stored material in the genebank. But in any genebank, the decision to regenerate should not be taken lightly.

Andres Godwin Sajise:

We first look into the database, to determine which accessions have low viability.

Marionette Alana:

(demonstrating at computer) We retrieve it using our database, so this is what we’re doing: we’re going to select ‘planting materials.’ We’re going to choose the species. It’s Oryza sativa. And then the storage site: we have base and active, but we’re going to choose ‘active’. And then we also have, one of the criteria is, we should check the viability. Viability should, if it’s less than eighty-five, and our threshold for the seed stock should be sixty. And then one more thing is, we should also check if it’s positive for nematodes or not. And since we’re already processing the current year, we should also exclude that one. And then just click ‘Process’, and the system will check everything we have in the collection.

Andres Godwin Sajise:

We plan our planting, based on the list we get from the database. These materials, we lay out them on the field based on the flowering time, so that no accessions adjacent to each other would flower at the same time. In this way, we avoid pollen contamination, although rice is self-pollinating, yet we still need to ensure that there is no pollen contamination between plants.

Andres Godwin Sajise:

We monitor the germination on the seed-beds, we count the seedlings that are healthy. We note down the flowering, so that we could determine the maturity of these materials.

Narration:

At IITA, this new generation of cowpea plants must yield seeds of high enough quality to survive storage. Their seeds must conform exactly to the seed file. They will be rejected if they’re unhealthy, too old or too young.

Andres Godwin Sajise:

In our monitoring, we do that regularly, we take note of the variations. We also do a lot of monitoring on the pests and diseases, because many of the sensitive accessions would require extra care. The more they are near to harvest, the more care that we give, to ensure quality seeds.

Narration:

Genetic drift, and other risks associated with regeneration, are minimised by using seeds of the highest quality. Seeds that have been dried effectively, checked for conformity and put into storage as soon as possible. The trick is to harness the biology of the seeds.

Fiona Hay:

Understanding all of this science helps us to do a better job. And, ultimately, what that means is that we'll be able to store the seeds for longer. So we'll be conserving the genetic diversity for longer, and that then means that we don't have to regenerate so frequently. And it means that we're avoiding the risk of genetic drift and so on, from these multiple cycles of regeneration. So all of this understanding of seed science helps us to do our jobs better.

End transcript: Video 3: seeds for the future

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Video 3: seeds for the future