The seed vigour test indicates the ability of seeds to emerge in varying environments of the field. It is generally believed, but not always true, that high germination percentage is associated with high vigour.
Significant differences can be seen in the crop stand raised from different seed lots having similar germination percentages. For example,
| Lot no | Lab germination (%) | Field emergence (%) |
| Peas 1 | 70 | 32 |
| Peas 2 | 72 | 69 |
A. Physical test:
Seed size: 100 or 1000 seeds drawn randomly and weighed in grams. The seed lot with high seed weight is considered as high vigour lot.
Seed density: Seed density and weight of the seed are directly correlated with seedling vigour. Seeds with higher density and weight, seedlings must be stronger and vigorous.
Physical soundness: Bold, clean seeds are vigorous, small and shriveled seeds are less quality, and low vigour seeds.
B. Performance test:
First count: The test is done along with the regular standard germination test. A number of normal seedlings germinated on the first count are counted, which indicates the quality of the lot. The number of normal seedlings gives an idea of the seedling vigour potential in the seed lots. Higher the number of normal seedlings in the first count, the greater the seed vigour.
Speed of germination: Seeds that are kept for germination have to be checked daily, and the number of normal seedlings removed.
Field emergence: The field emergence test was conducted in soil that was a sandy-clay with a moisture content of 16%. During field emergence (FE), the lowest air temperature was 6℃ and the highest air temperature was 16℃. Emerged seedlings were evaluated as a percentage.
Seedling growth rate and seedling dry weight: Total seedling growth is measured at a specific no of days after planting. Seed lots with high seedling growth rates have higher vigour.
- Seedling dry weight is dried at 110 oC for 17 hr and higher seedling dry weight is better seed vigour.
Paper piercing test (PPT): The principle of PPT is similar to the brick gravel test. High vigour seed lots are expected to produce strong seedlings which can pierce a paper. While seedlings from low vigour seed lots may not be able to pierce the paper.
Seedling vigour Index I and II: Seedling vigour index was given by Abdul-Baki and Anderson in 1973. This test is calculated by using the germination percentage of the lot and seedling growth parameters. i.e. seedling dry weight as per the following formula.
i. Vigour index-I: standard germination (%) x average seedling length (cm).
ii. Vigour index-II: Standard germination (%) x Average seedling dry weight (mg or g).
Also visit Seed dormancy, Seed pelleting, Seed born disease, TZ test, and Seed storage.
C. Stress test
Accelerated aging test (AA test): Exposing seeds to 40-50oC temperature and 100% RH for 2-8 days. Aged seeds were also sown in plastic pots filled with coco peat and an emergence test was conducted. Seed germination and emergence were recorded at 24-hour intervals until the numbers stabilized. 10 days for germination and 21 days for emergence test and Seeds having good germination after the AA test have high vigour and the capacity to perform well under field conditions.
Brick gravel test: This test was developed by Hiltner in 1911 to show pathogenic infection. In this test, we use brick gravel of 2-3mm diameter. In vigour tests on small seeds, a layer of brick gravel 2.5 cm thick is placed above the seed. The seedling emerges through the layer of brick gravel and is considered a high vigour lot.
Cold test (CT test): Cold test was conducted in 4 replications with 50 seeds for each replication. Samples were placed between moistened germination rolled papers with soil (70% of water holding capacity) and rolled the between papers were kept at 10℃ for 7 days, after which they were transferred to 25℃ for 6 days. 13 days after the start of the cold test, a seedling evaluation will be done according to ISTA rules.
In soil: The test is performed by planting seeds in unsterilized soil obtained from corn fields. A plastic box is used, and soil is 2 cm thick, and seeds are placed, and again unsterilized soil is added and 10 oC cold water I added, after 7 days it is transferred to 25 o c. Seedling counts are counted after 4 days after transfer.
Electrical conductivity: 3 replications of 50 seeds from reach lots are weighed and soaked in 250 ml of water in the dark.
- After 24 hours soak water was separated from the seeds by using cheesecloth and electric conductivity was measured.
- EC values measured were expressed as ℳsimens/cm/g after using the following formula for each replication of a seed lot.
- EC (Conductivity in soak water – Conductivity in deionized water)/weight of 50 seeds.
- Lower the value of electrical conductivity, the greater the seed vigour.
- Low-quality seeds leak electrolytes such as amino acids, and organic acids, while high-quality seeds contain their nutrients within well-structured membranes.
Cool germination: This test is mainly used for cotton, the seeds are kept in the germination chamber and maintain 18 oC constant temperature. It requires only one count done on the 6th day for acid-delinted cotton. 7th day for machine-delinted cotton.
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