Viability testing

One of the most important ways you can secure the conservation of PGRFA in your collection is to carry out regular viability testing. Keeping records of the conditions under which seeds were dried and tight controls on the conditions under which they are stored will help, but regular viability testing is your most reliable guide to when you need to regenerate, and put in a new, rejuvenated stock of seeds.

During the course of viability testing, some seeds will not germinate. It is important to evaluate these non-viable seeds. They can yield useful information about the causes of loss of viability. Are the seeds dead, dormant, quiescent or empty? Are there signs of disease, which requires treatment?

In the next documentary, scientists at IRRI and IITA show how they test the viability of seeds that have been in storage. Even if those seeds were dried and packed correctly prior to storage, and kept under ideal conditions during storage, once they come out of storage there are new considerations that can prevent seeds from meeting the target threshold for germination. As you watch the video, think about how the scientists at IITA and IRRI give their seeds the best possible chances of germinating.

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Transcript: Video 2: Monitoring viability

Narration:

These seeds have been in storage for many years. Will they still be capable of growing into new plants? Testing their ability to germinate is crucial, for the genebank to deliver seeds that will actually grow.

Olaniyi Oyotomi:

The moment the seeds are conserved in the genebank, in order to optimize the viability level, what we normally do is to ensure that, uh, at interval of time we check the viability, the expected viability of the seeds is 85% and above.

Marionette Alana:

Monitoring of seeds in the active collection is done every five years, and for the base collection, it is done every ten years.

Narration:

The tests involve growing out the seeds, to see what percentage will germinate. Water is essential, to re-hydrate the seeds, which had been dried before they went into storage. Now, the seeds must be placed into the right environment for germination to begin.

Marionette Alana:

So these are the germinators that we use for our viability testing, so the condition that we use is thirty degrees and the relative humidity is one hundred percent.

Narration:

Time will tell how many of these rice seeds will germinate. Everything that has happened to them so far will affect the success of the viability testing.

Olaniyi Oyotomi:

As long as we maintain all the conditions in the storage, that will allow the seeds to be alive, packaging them in an air-tight container, preventing moisture from coming in contact with the seeds, we ensure that the viability is still above the threshold of 85%.

Narration:

At IITA, the moisture round seedlings is held in by the sealed boxes. While at IRRI, the rolled paper towels are kept moist by the humidity of the germinator.

Marionette Alana:

So five days after putting the seeds in the germinator, we will now score the seeds based on their growth.

Narrator:

During scoring, it’s important to keep a numerical record of how germination is proceeding. Seeds that are growing normally, are counted and discarded. Seeds that haven’t germinated normally are given a second chance.

Marionette Alana:

In some cases, if there are still some seeds that have not yet germinated, we will then put them in a Petri dish and then enter the data in our database.

Narrator:

For some seeds, a few more days in a germinator is enough. But other seeds may need even more help before they will germinate. These are cowpeas, at IITA.

Kafayat Falana:

for those seed lots that are not germinated, we need to scarify them. With the use of a scalpel I puncture the seed coat of the seed, so the seed is able to imbibe water for germination processes.

Narrator:

In IRRI, they’re using a similar technique to encourage germination in wild relatives of rice. This counteracts dormancy – a natural behavior of wild species; yet another reason why, for some seeds, it may be hard to achieve the target viability threshold.

Fiona Hay:

So in the Genebank Standards, for crops that are quite easy to produce seeds and get high quality seeds, our viability standard is 85%. So this is lower than some certified seeds that would be sold for sowing, but it's still quite high.

Narrator:

Germination is complex process. Lots of biochemical reactions must happen, in the right order inside the seed. Not all seeds will germinate successfully. So why do genebanks set a standard as high as eighty-five percent for many species?

Fiona Hay:

It's important that we have the viability standard at that quite high level because when somebody requests this material, the material will have to be taken from the genebank and sent out. And sometimes there are delays there, and sometimes there might be phytosanitary treatments that have to happen. But basically by the time the user plants the seeds, and seeds, the germination of those seeds, the viability might be even lower. So they might just get 50% of the seeds they receive, actually germinating in their seedbed. So it’s important that we allow for that, that they’ll still get material that they can use.

End transcript: Video 2: Monitoring viability

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Video 2: Monitoring viability