• Definition- Those properties that determine the potential for rapid, uniform emergence and development of normal seedlings under a wide range of field conditions.

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• Attributes of high seed vigor
  1. Speed of germination
  2. Uniform germination and plant development
  3. Ability to emerge under crusted soil conditions
  4. Higher crop yield
  5. Yield stability

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• Processes associated with seed vigor
  1. Membrane degradation
  2. Reduced energy synthesis & respiration rate
  3. Declining germination %
  4. Shortened storability period
  5. Slower growth rate & development
  6. Lack of uniformity
  7. Reduced plant resistance
  8. Lower yield
  9. Poor emergence in the field
  10. Occurrence of abnormal seedlings

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• Evaluation for seed vigor
  • Characteristics of an ideal vigor test
    1. Can be conducted rapidly
    2. Useful with single seeds or larger quantity
    3. Can detect small differences
    4. Inexpensive
    5. Uncomplicated
    6. Objective
    7. Reproducible
    8. Correlates with field results

  • Factors that influence seed vigor
    1. Genetic Constitution
       • Hybrid vigor
       • Hard seeds
       • Susceptibility to mechanical damage
       • Chemical composition
    2. Environment During Seed Development
       • Ambient temperature
       • Humidity
       • Soil moisture & fertility
    3. Seed Maturity
    4. Postmaturation-Preharvest Environment
    5. Seed Size & Density
    6. Age & Deterioration
    7. Microorganisms

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• Types of Seed Vigor Tests vig_test.gif
  1. Accelerated Aging Test
     • Expose to high temperature and humidity
     • Conduct Warm Germination Test
     • Simulates long-term storage
  2. Cold Test ct_vig.gif
     • Conducted in soil
     • Temperature at/or near minimum germination temperature
     • Evaluate emergence %
  3. Conductivity Test cond_age.gif
     • Evaluates for leachates due to cellular membrane leakage
  4. Cool Germination Test
     • A germination test conducted at low temperature
     • Used principally with warm-season crops
  5. Seedling Growth Rate Test
     • Evaluation of plant tissue from Germination Test minus seed tissue
  6. Seedling Vigor Classification Test
     • "Normal" seedlings are classified into "Strong" and "Weak" categories
  7. Tetrazolium Test
     • Based on reaction of hydrogen to dehydrogenase enzyme
     • Results in the formation of Formazan which is evaluated for intensity
  8. Speed of Germination
     • An Index of Vigor value is calculated
  9. Brick Grit Test
     • Simulates crusted soil
     • Also known as the Hiltner Test
  10. Osmotic Stress
      • Seeds are germinated in solutions with specific osmotic potentials
      • Simulates drought conditions
      • Probably works best with small-seeded crops
  11. Respiration Tests
      1. Adenosine Triphosphate (ATP) Test
      2. Glutamic Acid Decarboxylase (GADA) content

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• Standardization of Vigor Tests
  • Influencing Factors
    • Reproducibility
    • Dormancy

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• Attributes of Vigor Tests
  • Provides farmers with additional information and confidence in the seed
  • Serves a quality control mechanism for seed companies
  • May serve as useful information to agronomists, legal consultants, etc.

References:

Principles of Seed Science and Technology. 3rd Ed. L.O. Copeland and M.B. McDonald. Chapman and Hill, New York, 1995