VIII. Monitoring Accessions

What is meant by monitoring?

As previously explained, the viability of the seeds will decrease during storage over long periods. The number of seeds of each accession held will also decrease as seeds are removed for testing and in the case of active collections, when seeds are distributed. Both viability and seed number must be monitored during storage.

Why must accessions be monitored?

Seed viability and number of seeds of each accession in the store must always be known with reasonable accuracy. Only then can accurate decisions on regeneration be made.

When should seeds be monitored?

The number or weight of seeds in store should be monitored every time seeds are removed from the genebank. Seeds should not be removed if only a few seeds remain. The viability should be monitored at regular intervals. This interval will be determined by the curator depending on the species, viability of the seeds at the start of storage, moisture content and storage conditions. The IBPGR Advisory Committee on Seed Storage recommends that seeds stored under the preferred standards in base collections should be monitored at least every ten years and that those with either poor storage life or poor initial viability in base collections, together with all seeds stored in active collections, should be monitored every five years.

How should accessions be monitored?

The number or weight of seeds can be monitored automatically by checking in the genebank management data file and need not be described further here. The viability can be monitored by doing a fixed sample size germination test as already described in Section V or using a sequential method as explained here. Both tests use the same germination conditions and differ only in the number of seeds used for the test and the interpretation of the results. On average the sequential germination test uses fewer seeds and the IBPGR Advisory Committee on Seed Storage has recommended it for monitoring collections in genebanks.

STEP 1. DETERMINE WHICH ACCESSIONS REQUIRE MONITORING

1. The fact that accessions will be entered into the genebank in an irregular pattern, with many being entered at the same time after harvest or a collecting mission and few accessions being entered at other times, means that monitoring of accessions will also be in an irregular pattern.

2. Every week check the genebank management data file to see which accessions require monitoring during that week.

3. Prepare a list of all accessions by number, which require monitoring during the week.

4. If there are many accessions which require monitoring at the same time, make subgroups of about 20 accessions of similar species which can be handled with the same technique and do these on different days to spread the work.

5. If there are few accessions which require monitoring at the same time, it may be more efficient for them to be grouped and the monitoring done once a month.

Notes and Examples

Do not handle too many accessions at the same time. Availability of staff and equipment determine the number of accessions handled at one time.

Samples needing monitoring within one or two weeks can be grouped together for convenience.

1. Check each accession number in the management data file to make sure that sufficient seeds are available for the test. If few seeds are available, do not test now because the material will have to be regenerated soon.

2. Make a list of each accession number, its location in the seed store and any data relating to the methods and conditions used for the germination test.

3. Remove the seed containers from the store and leave at room temperature, until the container has warmed up, before opening.

4. Count the number of seeds needed for the test from each accession. Work in a dehumidified room, if possible, and close the containers as soon as the seeds are removed to prevent the seeds absorbing moisture from the air.

Notes and Examples

Large containers may take several hours to reach room temperature, but it is important that cans should not be opened before room temperature is reached or condensation may form directly on the seeds and cause changes in moisture content.

Two methods are recommended by the IBPGR Advisory Committee on Seed Storage:

Fixed sample size germination test

1. Do a fixed sample size germination test using a minimum of 200 seeds sown as two replicates of 100 seeds and follow the techniques already described in Section V.

2. Calculate the percentage germination from the results of the test.

3. If it is above 90%, accept the test as valid and use this value as the true viability.

4. If the result is 90% or below, repeat the test using a further 200 seeds following the same procedures.

5. Calculate the mean percentage viability from the results of the two tests and use this as the overall test result.

6. Compare the final result of this test with the results of the previous test and decide whether regeneration is necessary, according to the following criteria:

If the percentage germination has decreased to 85 or less, regenerate the accession.

If the percentage germination is above 85, the curator will plan the next monitoring test date depending on the germination percentage.

Notes and Examples

The fixed sample size germination test is done using the standard techniques for the species in your genebank, as already explained in Section V.

Filter paper, paper towelling or rice straw paper
Plastic bags
Petri dishes or other containers
Water
Forceps
Incubators
Labels
Permanent markers
Sand
Pots or trays
Tools for planting

1. A sequential germination test uses the same conditions and techniques as already described for the fixed sample size germination test, but uses less seeds for each replicate. The replication is done in a sequential way when necessary and thus not all replicates are tested at the same time.

2. The number of seeds required for each replicate can vary; the more seeds and replicates, the more accurate the test. It is recommended that a sample should consist of 40 seeds per replicate as a minimum.

3. Do a germination test using the conditions and methods as already described in Section V using one replicate of 40 seeds.

4. Count the number of seeds germinated.

5. Compare the results of the test with the number germinated in Table 3, which shows the germination test plan for the 85% regeneration standard using a sample size of 40 seeds per replicate.

6. Look at the line with the value of 40 in the first column (number of seeds tested).

(i) If the number of seeds germinated is 29 or less, the accession will require regeneration as explained in Section X.

(ii) If the number of seeds germinated is more than 29, then the test will have to be repeated with another sample of 40 seeds exactly as above.

8. Count the number of seeds germinated in the second test and add this to the result of the number of seeds germinated from the first test. Add the total number of seeds used for both the samples.

9. Compare the results of the test with the number germinated in Table 3 as before. Look at the line with the value equal to the total number of seeds used for all tests (80) in the first column (number of seeds tested).

(i) If the number of seeds germinated is 64 or less, then the accession will require regeneration.

(ii) If the number germinated is between 65 and 75, the accession will require testing again with another sample of 40 seeds.

(iii) If the number germinated is above 75, then the viability of the accession is still above the regeneration standard and the accession does not require regeneration.

Notes and Examples

The sequential test has an advantage in that it uses less seeds but is of a similar accuracy to the fixed sample size germination test. The actual germination test conditions and procedures are the same for both types of germination test, the only difference being in the number of seeds used. The cost of storing germplasm is high; therefore, seeds should not be wasted. The cost of regeneration and the possibility of selection and loss of accessions during regeneration are high. Therefore, test results should be accurate and indicate when regeneration is needed. A balance has to be found between using enough seeds to be accurate and using too many wastefully. This balance is found in the sequential germination test.

If seeds are thought to be of high viability or questionable, it may be simpler to set up the first two sequential replicates together (2 x 40) because as can be seen in Table 3, a second test will probably be necessary. It is easier and quicker to set up two tests together than to repeat the whole process after the results of the first test are known. There is then no delay in getting the results of the second test. When you know prior to testing that the seeds are probably in poor condition, one test is sufficient to show that regeneration must be done.

It is obvious that the test is open-ended and if the answer always fell within the range where the accession required testing again using another sample, a large amount of seeds would have to be used to determine whether regeneration is necessary. Therefore it is suggested that in circumstances where no definite decision can be made regarding regeneration, the test should be terminated when ten samples have been tested. This uses 400 seeds, which is the same as in the fixed sample size germination test for accessions of less than 90% viability. Results can then be converted to percentage germination and a decision on the need for regeneration can be made.

Filter paper, paper towelling or rice straw paper
Plastic bags
Petri dishes or other containers
Water
Forceps
Incubators
Labels
Permanent markers
Sand
Pots or trays
Tools for planting

Table 3. Modified sequential germination test plan for 85 percent regeneration standard for groups of 40 seeds

Number of seeds tested	Regenerate if number germinated is less than or equals:	Repeat test if number germinated is between:	Store if number germinated is more than or equals:
40	29	30 - 40	-
80	64	65 - 75	76
120	100	101 - 110	111
160	135	136 - 145	146
200	170	171 - 180	181
240	205	206 - 215	216
280	240	241 - 250	251
320	275	276 - 285	286
360	310	311 - 320	321
4001	340		341

¹ When 400 seeds have been tested, the test can be terminated because enough tests have been done for a practical decision to be made.

Ellis, R.H., Roberts, E.H. and Whitehead, J. (1980). A new, more economic and accurate approach to monitoring the viability of accessions during storage in seed banks. Pl. Genet. Resources Newsl., 41: 3-18.