Scoring germination

It is good practice to score germination tests and keep careful records of how many seeds have germinated normally, how many have germinated abnormally, and how many required some kind of intervention to encourage germination. The germination test will continue until all germination stops: the time this takes will depend on the species you are dealing with (and some wild species can take many months to germinate!).

Watch this video, a short clip from the longer video entitled ‘monitoring viability’ that you first watched in module 2. Now that you have considered germination in more depth, you should be able to approach the methodologies used by the two genebanks with a deeper understanding. As you watch, think about what decisions have been made by the two genebanks about how to carry out germination tests, and how these decisions relate to the underlying biology of the two crops.

Download this video clip.Video player: Video 1: Germination testing
The image is a still from the video. It shows a technician at the International Institute for Tropical Agriculture putting closed plastic containers of germinating seeds onto the shelves of a temperature-controlled germination room.
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Transcript: Video 1: Germination testing

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. 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 germination.
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.
Narration:
During scoring, it’s important to keep a numerical record of how germination is proceeding. Seeds, which 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.
Narration:
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.
End transcript: Video 1: Germination testing
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Video 1: Germination testing
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Please write your comments on how this viability test is carried out. You should spend up to ten minutes on this. If your reflections on the video raise any questions, please post them on the Forum, where the course moderators will be able to help you.

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Discussion

In IRRI, they use a between papers (BP) approach. In IITA, the cowpeas are laid on top of papers (TP). In both genebanks, temperature and humidity levels are optimized for the crop: this is achieved in species-specific ways. In both genebanks, the scientists score germination by counting and discarding the germinated seeds. They keep careful records about numbers of seeds that germinate correctly, abnormally, or not at all. In IITA, scarification is used to encourage seeds that do not germinate, in order to maximise their chances of successful germination. Scarification is not necessary for cultivated rice, although it is used by IRRI for wild relatives of rice.

Germination requirements: time

What is ‘normal’ growth?