Based on our experience at the Seed Centre this 2200 word document will be useful when a Local Seed Network needs to find out how fertile their seeds are.
Procedures Manual: Viability Testing
As our network is a non-government, non-profit organisation, a careful balance has to be maintained between limited resources and the accuracy of these tests. Our testing procedure is not strictly scientific and serves mainly to guide rather than "convince". However we have standardised our procedures over the years and so the viability percentage that is recorded on the seed packets is consistent.
There are threee main ways that we conduct tests. The majority of seeds are tested on paper towels.
1. Paper Towel Testing: The criteria for this type of testing is adequate ventilation and moisture. Light is not necessary. Seeds are to be tested in their relevant growing season. See the sub-tropical sowing guide attached.
Use for all seeds except beans, melons and gourds.
2. Testing in small bowls: Beans are to be sprouted in receptacles such as bowls, saucers, and cups. Corn and peas have successfully sprouted in this manner too although they give a similar result in paper towels.
3. Testing in pots: Melons, gourds and other cucurbits are best sown in pots because it seems some kind of enzyme action in the soil is needed for better germination. Even corn and beans which need warm soil may be tested this way especially in winter when they need warmth. The pots can be kept on top of a water heater or in a glasshouse for this purpose.
Paper towel and bowl testing are only indicative of the viability of the seed lot and not of their vigour, i.e., the seeds capacity to push up through soil to grow.
Procedure
1. Collect from the shelf just inside the seed bank the box of equipment labelled "Viability Testing" containing
¥ plastic sheet for protecting the work surface from water
¥ small oblong plastic bags, hole-punched for ventilation
¥ pot labels/tags (white plastic, as used by nurseries)
¥ pens (red and blue), soft black pencil, rubber, ruler, sharpener
¥ work sheet folder, adhesive labels and calculator
¥ unbleached paper towels
¥ atomiser with pure water
¥ office baskets/trays (plastic coated wire type).
2. Collect seeds for testing. Put carrot and parsnip seeds in the fridge for twenty four hours to vernalise them.
3. Fill in seed lot details on the work-sheet:- accession number and variety name from the label on the seed bag as well as the date the test has commenced.
4. In soft lead pencil write the accession number and variety name on the pot-tags to correspond with the entries on the work-sheet. If the pot-tags have been used clean off with the rubber.
5. Lay plastic sheet down on a table and place 6 pieces of paper towel on it.
6. Place each pot-tag to the left of each paper towel. The habit of working from left to right consistently reduces the possibility of error such as a wrong tag in the seed lot being tested.
7. Select a random sample from the seeds by putting the whole lot out on a sheet and dividing into two, then mix one half and divide into two again, then repeat this again and again until you have approximately the number of seeds required.
8. Spread seed out as evenly spaced as possible, for ease of counting, onto the paper towels - but not too close to the edges.
CRITERIA FOR THE NUMBER OF SEEDS TO TEST FROM EACH SEED LOT:
a) no more than a pinch from the bag as some seed lots that come in are very rare and can't be used up in tests where it could be grown out directly instead
b) even if there is a large quantity of seed available in the lot, too many seeds in the test makes an endless chore of counting the sprouts each week
Number of seed varies with size of seed. Some approximations:
Poppy too small to count (approx. %)
Lettuce 40 - 60 Tomato 30 - 45
Sweet corn 20 - 30 Spinach 10 - 15
9. Count the number of seeds on each towel and enter on the work sheet.
10. Spray the seeded sheets lightly to "bed down" the seed to the paper towel. Take care to keep moisture away from the bags of seed you are working with. Place a top sheet of paper towel over and spray it until evenly and thoroughly damp (but not dripping wet as seeds will rot or go mouldy).
11. Roll the "sandwich" of towels with seed 2 times over as per illustration.
If the paper towel is rolled over too many times the seeds are likely, again, to rot or go mouldy. Carefully pick up and place on the ruler and slide into the hole-punched bag so that it rests along the bottom seam.
Place the relevant pot tag inside.
12. Place each test sample in the compartments of the wire office baskets. One sample goes in at each end with 2 being placed in each compartment from there. The samples are to sit up vertically.
13. Samples must be checked daily for dampness. If drying out, squirt into the bag with the atomiser onto the towelling without removing it from the plastic hole-punched bag (to reduce excessive handling). Keep baskets positioned up from a surface to allow air to circulate under and around them.
14. Every 7 days for the 4 week period take each sample out, one at a time, unfold carefully on a flat surface, taking off the cover sheet of towelling and count the number of seeds sprouted. It's much easier to count the sprouts by leaf form than root form. Replace the cover sheet and atomise if needed. Then roll up, place back in the bag and return to its compartment. Enter the count on the work sheet. Record any unusual event such as presence of mould, insects, seeds rotted etc.
15. Samples can be grown or thrown after the 4 weeks, or earlier where maximum number of seeds germinated has occurred.
Some approx. sprouting times:
Lettuce 4 - 10 days Parsley 3 - 4 weeks
Tomatoes ditto
16. Using a calculator ascertain the % of viability by dividing the number of seeds sprouted by the number of seeds tested. Please take care in interpreting the decimal point. There is a big difference between 4% and 40% !!! Write the % of viability and the month and year of test, in red pen preferably, on a small adhesive label and affix to the bag of the relevant seed lot. Also enter on the work sheet.
Procedure for bowl testing of beans, or corn and peas
For this test the seeds need to be soaked overnight prior to testing.
1. Collect the seed lots and enter details on the work sheet i.e. accession number, variety names, test commencement date and numbers of beans being tested from each lot.
CRITERIA FOR NUMBERS OF SEEDS TO TEST: The same rationale applies as for smaller seeds. Generally, where the seed lot is of a small quantity, use 5 - 8 beans. If the seed lot is of a large quantity use 8 - 12 beans.
2. Write the accession number of each seed lot on small adhesive labels and affix to the receptacle that will be containing them. Place the corresponding seeds in that.
3. Pour tepid water over the seeds in their receptacles for the overnight soak.
4. Next day drain off the water from each receptacle, fill again with room temperature water as a rinse and drain off.
5. Remove seeds from the receptacle and place an unbleached paper towel, folded over in quarters, into the bottom of the receptacle. Spray with the atomiser until the towel is quite wet. Place seeds in the relevant receptacle and if the weather is hot and or dry, lightly place a dampened paper towel on top.
6. Check daily for wetness and atomise if needed. If seeds show signs of too much wetness (mould on the seeds or paper towel, smelly, etc.), remove the paper towel that has been lightly covering them. Viable seeds tend to sprout after about 3 - 5 days. Non-viable beans rot and smell badly (has-beens!).
7. With beans, records of sprouting are better done daily and maximum germination has often occurred within or by one week.
8. Upon completion of tests sprouts may be eaten, grown out or dumped.
9. With a calculator ascertain the % of viability. Divide the number of seeds sprouted by the number of seeds used for the test. Please take care with the interpretation of the decimal point. There is a big difference between 4% and 40%!!! Enter the % on the work sheet.
10. Write the % of viability and the month and year of the test on a small adhesive label, preferably in red, and affix to the bag containing the relevant seed lot.
Procedure for testing beans, corn, peas and cucurbits
Our experience with testing larger seeds in paper towels indicates that a more accurate % of viability can be gleaned from tests conducted in sand in pots. Perhaps this is due to an enzyme requirement on the part of these seeds. Experienced growers recommend that very hot water be poured over these seeds beforehand.
1. Collect Viability Testing box of equipment, seed lots to be tested and number of pots required.
2. Fill in the seed lot details - accession number, variety name and date of commencement of test on the work sheet.
3. Using a soft lead pencil write the accession number, variety name number of seeds and date of test on the white pot tags.
4. Set up the pots required with seed raising mix (not potting mix) and insert a pot tag into each. Sand mix level in the pot initially ought to fall about a centimetre below the rim.
5. Take the number of seeds to be tested and plant about a centimetre deep for melons, two centimetres deep for gourds, into the pots. Cover over with soil mix to fill the pot and water with a light sprinkling being sure that sand is wet.
6. The pots will for the most part require a gentle watering morning and afternoon. Be sure to place test pots in a place safe from cats, dogs, slugs, etc., and where they will receive at least 3 - 4 hours of sun.
7. Record the number of sprouts every seven days from commencement of test on the work sheet until maximum germination has occurred. Generally 2 - 3 weeks would see this out.
8. Ascertain % of viability as already outlined, mark on the work sheet and on an adhesive label (with the month and year of test) and affix the label to the appropriate bags of seed lot.
Posterity Sample Procedure
We keep a small sample of each viable lot of seeds for posterity in a fridge. They will be used in the Seed Savers Trial Gardens. Also, especially with larger seeds, they will be a good comparitive reference for future returned lots.
1. Collect the seed lots from the last round of viability testing.
Sort the samples into two groups according to the percentage of viability. Generally, seed lots 50% viability and over will be used to take a sample from. 49% and lower viability seed lots will be sent out for regeneration.
The exception to this rule is for melons and gourds which rarely exhibit high viability percentages. For these, include seed lots with over 30% viability .
2. From each seed lot take 10% out of the contents where viability is 70% and 20% out of those from 50% to 69%. Place in a small plastic press-seal bag. Affix adhesive labelling with the same details as on the original bag's label, along with the percentage of viability, the month and year of the viability test written in red pen.
For corn and sunflowers the minimum number of plants required for true genetic representation is 100. Add more seed than this on a scale according to the sample's viability. For example, if the viability is 60%, then about 170 seeds would be needed to produce a plot of 100 plants.
3. Sort the posterity samples into Plant Groups such as beans, lettuce, flowers, spinaches, etc., and fill out an index card with the following information:-
BEANS POS. SAMPLE '99
#005 Kentucky Wonder Har. 2/99 62% 6/99
#1571C Betty's Zebra Rec. 8/98 89% 6/99
#3427BA Hyacinth Rec. 11/98 58% 6/99
4. Insert the samples and index into the appropriate sized PVC coated bag ensuring the index can be read through the front of the bag. Put in a press-seal bag of blue silica gel and a number of oxygen absorbers.
The bag of silica gel has to be visible from the back so we can see any colour change due to moisture absorption. For a PVC-coated bag with a lot of seed samples in it, use one of the bigger press-seal bags of silica gel and around five to seven sachets of oxygen absorbers. Generally though, posterity samples being small, a small PVC coated bag with the smaller press-seal bag of silica gel and around two to four sachets of oxygen absorbers will suffice.
5. Heat seal the bag of samples taking care to squeeze as much air out of the bag as possible the moment before sealing, and to ensure that the seam before and after sealing is not wrinkled. Air will leak back into the PVC coated bag through the wrinkling. Store in the buckets in the fridge.
THANK YOU, JUDE AND MICHEL
Subject Local Seed Networks
Regional relation Global
Audience localseed - teacher
Physical format Web pages
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