Why is seed viability important

Seeds of some species are more tolerant and germinate in a wide range of conditions but complete germination can only be achieved under optimum conditions. Seed dormancy is seen when seeds imbibe water under suitable temperature and light for germination but germination does not occur. Las Cruces, NM.

Genebank standards for plant genetic resources for food and agriculture. International Rules for Seed Testing. International Seed Testing Association. Available from: www. Available in English 1. The Species Compendium release 1. Date accessed 09 April Crop Genebank Knowledge Base. Home About this site Contributors Copyright Contacts. Sample preparation Viability and monitoring Field management. Establishment Monitoring.

Figure 3: Sizing paper towels for petri dishes: cut a folded paper towel in half with sterile scissors, then trim the long edge of the paper towel to fit perfectly in a petri dish. With a sterilized hand or an inverted funnel, snug substrate paper into the container Figure 4. Add an appropriate amount of distilled water if distilled water is not available, use boiled and cooled water to completely moisten the paper without soaking it Figure 5.

We have found that typical containers with a double-folded paper towel require from 2 to 6 ml of water, depending upon the size. Spread the seeds uniformly on the moistened substrate, ensuring that none of the seeds touch each other Figure 6.

Close the lid, and place the container inside a loosely fitting sandwich bag to help ensure additional moisture retention Figure 7. You want to prevent loss of moisture, but still allow diffusion of oxygen, which the seeds will need when germinating and respiring. Figure 5: A good workstation flow showing labeled petri dishes, syringe for watr application, sterile water, and disinfected seeds; from here petris will go directly into their places in the seed germination cabinet.

Figure 6: Lablab seeds distributed on moistened paper towel with tweezers they don't need to be in neat rows, but they must not touch each other, in case one is contaminated. I used 25 seeds in each petri for my mock experiment, and the rows helped to ensure that all 25 made it into each dish.

Figure 7: Closed petri dish with plastic bag loosely sealing it and loose edges tucked under to preserve moisture but allow air exchange.

Place the containers in your seed germination cabinet, or in a warm area where some light is present. Every day, or every other day, count, record, and remove germinated seeds.

Germination is defined as the clear and unobstructed emergence of the radicle, or seedling root, from the seed coat Figures 8, 9. Figure 8: Radicle emergence of amaranth seed after 1 day; these would be counted as germinated and removed. Figure 9: Radicle emergence of amaranth seed after 1 day; these would be counted as germinated and removed. Substrates will most likely need to be re-moistened during the course of the test; be sure to give containers with the same seed types an equal amount of water, making note of the amounts.

Most seed germination experiments should be run for up to 14 days but some grass species may require up to 28 days to germinate. You may decide to run your experiment shorter or longer depending upon the type of seed, and if all seeds germinate. During the test, carefully remove and discard any seeds that show signs of contamination or decay.

In the between paper method, ordinary paper towels are used as the substrate and also act as the container to hold the seeds. Cut a paper towel to size to adequately hold all the seeds of the replication in neat rows on the towel.

Using a pencil or permanent marker, label one edge of the paper towel with the type of seed being tested and the number of the replication. Moisten but do not soak the paper towel with distilled water. Next, place the seeds in rows on the moist paper towel, leaving a 3 cm gap from the top and side edges, and ensuring that the seeds do not touch each other.

Any extra space should be at the bottom of the paper towel, which will be immersed in water. Cover the seeds with another moist paper towel and roll the paper towels from the nonlabeled edge Figure Use a paper clip or rubber band to hold the newly formed tube together. The seeds will be inside the tube, held by friction between the two layers of moist paper towel.

Place the bottom of the paper towel tube in a deep-bottomed plastic tray with enough water to ensure that all paper towel tubes are in contact with the water Figure Place the tray of paper towel tubes in your seed germination cabinet or in a warm area where some light is present.

Preharvest environment of high humidity and warm temperatures can also cause loss in seed viability and vigor. Seed mechanical damage, whether induced by harvesting or conditioning equipment, as well as improper storage conditions are among the factors that adversely affect seed vigor. In addition, genetic factors such as hard-seededness, resistance to diseases, and seed chemical composition influence the expression of seed vigor.

The general strategy of determining seed vigor is to measure some aspects of seed deterioration or weaknesses, which is inversely proportional to seed vigor. Cold test, accelerated aging test, electric conductivity test, seedling vigor classification, and seedling growth rate are among the tests that are used to measure seed vigor.

In addition, the tetrazolium TZ test can be used as a vigor test by classifying the pattern of stained seeds into high, medium and low quality. Below is a brief description for some of the most common seed vigor tests that are used for various crops including corn, soybean, field beans, peas, grasses, vegetable seeds, and other crops. At the end of the cold period, the test is transferred to a favorable temperature for germination e. The percentage of normal seedlings is considered as an indication of seed vigor.

Vigorous seeds germinate better under cold environments. High vigor seeds are expected to tolerate high temperatures and humidity and retain their capability to produce normal seedlings in the germination test. This test measures the integrity of cell membranes, which is correlated with seed vigor. It is well established that this test is useful for garden beans and peas. Roll the paper loosely towards the end with the label. Notes and Examples Do not roll the paper too tightly because the compression and lack of oxygen resulting from this can cause the seedlings to develop contorted roots and shoots.

These are hard to separate from abnormalities caused by genetic factors. Place the rolled papers inside ventilated plastic bags or boxes.

Notes and Examples Oxygen is essential for respiration during germination. Therefore, any containers used should be adequately ventilated.

Put these in an upright position in wire baskets or plastic boxes. Keep the paper moist with water. Notes and Examples Root and shoot development is geotropic. Placing the rolled papers in an upright position allows seedling development in the natural vertical position. Germination in sand 1. Pack clean sterile sand into pots or trays with drainage holes in the bottom. Water the sand until it is moist. Do not use excess water.

Notes and Examples Fine sand should be used. Make sure that the sand is clean by sterilizing before use. Quarry or river sand is better than shore sand, which must be washed thoroughly to remove all salt.

Make holes in a regular equidistant pattern at about the same depth as the size of the seeds for each replicate of the seeds. Ideally, the distance between holes should be at least three to five times the seed diameter.

Prepare a label with the accession number, date of sowing and replicate of the test and place in each pot or tray. Notes and Examples Germination in sand is especially useful for large seeds which are too large to be germinated in petri dishes or too heavy for the between paper method.

Fill seeds from each replicate into the holes and cover with sand. Water the sand again to cover the seeds, but do not make it too wet. Notes and Examples Sprinkle with water slowly, so that the seeds do not float out from the holes and become mixed.

Bottom watering is better than top watering. STEP 4. Place the prepared germination tests under the light and temperature conditions which were determined in Step 1. Keep the substrate moist during the test with water, but do not over-water.

Run the test for a sufficient period to determine whether the seeds have germinated, or are dead or dormant. A fixed interval can be used based on previous experience, but the time taken to germinate will vary among species and accessions of the same species.

Notes and Examples Seeds absorb most water during a rapid imbibition phase at the start of the test. Make sure that there is enough water at this stage but remember that too much water at a later stage can limit the oxygen for the seeds and also lead to rotting. STEP 5.

Seeds sown on top of paper can be counted either through the transparent cover or after removing the cover of the container. For those between paper, unroll the paper carefully to avoid tearing the paper or damaging the roots of the young seedlings.

Count and record the number of normal seedlings in each replicate. Count and record the number of abnormal seedlings in each replicate. Examples of the types of abnormal seedlings found in different species have been described by ISTA b.