Time between harvest and storage
So far, you have learned the danger of waiting too long to harvest - we don’t want to allow seeds to disperse and be lost. You have learned that seeds should not go into storage when they are immature, but it is also important that they also should not go into storage when they are too old. Watch the animation, which is based on data about the fate of seed lots regenerated by a genebank in 1990. As you watch, think about what was happening to the longevity of these seeds as time went by.
Transcript: Video 2: processing time and viability
In 1990, a fresh accession of seeds was checked in to a genebank.
Some of these seeds were processed in less than 6 months.
Some were processed in less than a year.
Others were left between one and two years before they were dried, cleaned, packed and placed into storage.
What difference did this delay make to their long-term viability once they had gone into storage?
Let’s start with the seeds that were processed within six months.
After 3 years, the results of germination tests ranged from fifty to 100%. The lower results are probably because some of the seeds were dormant.
After 12 years, this situation has improved: most of the dormancy has worn off.
After 16 years, the results are satisfactory - about 85 to 98%.
Even after 20 years, viability has not declined a lot.
What about the seed lots which went into storage after 6 months to one year?
Once again, the initial results could perhaps be explained by dormancy.
But by 10 years, dormancy can’t explain why the lowest viability has dropped to a measly 30%.
And after 16 years, when you’d expect dormancy to have passed, there is still a wide spread of viability.
At 20 years, although some seeds are highly viable, the results are more patchy than for the seeds that were fresh when they first went into storage.
Much the same is apparent for seeds that waited between one and two years before they went into storage.
There’s a noticeable tendency for these seeds to perform less consistently in germination tests compared to the viabilities of the seed lots that had been placed into storage in less than 6 months.
These results suggest that when freshly harvested seeds arrive at your genebank, there’s no time to waste.
Please use the box to note down what happened to seed lots put into storage after 0-6 months, 6-12 months, and 1-2 years. What implications does this have for your own genebank? You should spend up to ten minutes on this. If your reflections raise any questions, please post them on the Forum, where the course moderators will be able to help you.
When you are ready, press 'reveal' to see our comments.
Discussion
Seed lots put into storage up to six months after harvest did not, at first, germinate as strongly as perhaps you might expect. This may be because some seeds were still dormant: a little longer in the drying room might have broken this dormancy. Nevertheless, these seeds show strong viability over the long term. Seed lots put into storage within a year of being harvested were able to germinate vigorously, even after more than twenty years of storage. By contrast, in seed lots which had to wait years before going into storage, there is a noticeable tendency to perform less well in germination tests when they came out of storage. These data show that delays in processing seeds before storage can compromise longevity and viability.
Dried to perfection