Model Answer
0 min readIntroduction
Seed testing is a critical component of agricultural production systems, ensuring the quality and reliability of planting material. It is a series of laboratory procedures performed to evaluate the physical and genetic qualities of seed lots. With the increasing demand for food and the challenges posed by climate change, the role of high-quality seeds in enhancing crop yields and resilience is paramount. India, being an agrarian economy, places significant emphasis on seed quality control, as evidenced by the Seed Act, 1966, and subsequent amendments. This answer will detail the objectives of seed testing and the methods used to assess seed viability, vigour, and genetic purity.
Objectives of Seed Testing
The primary objectives of seed testing are:
- To determine the quality of seed lots: Assessing germination, vigour, and genetic purity.
- To provide information to seed producers and users: Enabling informed decisions about seed selection and usage.
- To ensure compliance with seed quality standards: Maintaining the integrity of the seed supply chain.
- To protect farmers from low-quality seeds: Contributing to sustainable agricultural practices and food security.
- To facilitate international trade: Meeting phytosanitary requirements and ensuring seed quality for export.
Seed Viability Testing Methods
Viability refers to the ability of a seed to germinate. Several methods are used to assess it:
- Tetrazolium Chloride (TTC) Test: This biochemical test assesses the metabolic activity of seeds. TTC reduces to a red-colored formazan in viable seeds, indicating living tissue. Non-viable seeds show no reaction. It's rapid and cost-effective.
- Germination Test: The most common method, involving placing seeds on a suitable medium (e.g., filter paper, sand) under controlled temperature and moisture conditions. Germination percentage is calculated after a specified period (usually 7-14 days).
- Emergence Test: Seeds are sown in soil under controlled conditions, and the percentage of seedlings emerging is recorded. This simulates field conditions more closely than the germination test.
Seed Vigour Testing Methods
Vigour is a broader term than viability, reflecting the seed's ability to germinate rapidly and uniformly under favorable conditions. Vigour tests evaluate these aspects:
- Cool Germination Test: Seeds are germinated at low temperatures (e.g., 10-15°C) to assess their ability to overcome chilling stress. A lower germination percentage at low temperatures indicates lower vigour.
- Accelerated Aging Test: Seeds are exposed to high temperatures and humidity for a short period (e.g., 42°C for 72 hours) to simulate premature aging. The subsequent germination percentage is compared to the control to assess vigour.
- Electrical Conductivity Test: Measures the leakage of ions from seeds. Higher leakage indicates membrane damage and lower vigour. This is a rapid, non-destructive test.
Seed Genetic Purity Testing Methods
Genetic purity ensures that a variety remains true to its original genetic makeup. This is crucial for maintaining the desired traits and yield potential.
- Visual Inspection: Comparing seed characteristics (size, shape, color) with the parental variety.
- Grow-Out Test: A small number of seeds are planted, and the progeny are observed for any variation in traits. This is the most reliable method for assessing genetic purity.
- Molecular Marker Analysis: DNA-based techniques (e.g., PCR, DNA fingerprinting) are used to identify specific genetic markers that characterize the variety. This is increasingly used for accurate and rapid purity assessment. The National Seed Bank maintains repositories and uses these techniques.
| Test Type | Method | What it Measures | Advantages | Disadvantages |
|---|---|---|---|---|
| Viability | Tetrazolium Chloride | Metabolic activity | Rapid, Cost-effective | Doesn't predict field performance |
| Viability | Germination Test | Germination percentage | Simple, widely used | Time-consuming |
| Vigour | Accelerated Aging | Seed deterioration rate | Rapid | Needs calibration |
| Genetic Purity | Grow-Out Test | Genetic stability | Reliable | Time-consuming, requires land |
The Seed Act, 1966, and the Seed (Control) Order, 1988, govern seed quality control in India. The National Accreditation Board for Seed Certification (NABC) oversees seed certification and testing activities.
Conclusion
Seed testing is a vital process for ensuring the quality and reliability of seeds, contributing significantly to agricultural productivity and food security. The methods discussed – viability, vigour, and genetic purity assessments – provide crucial information for seed producers, regulators, and farmers. With advancements in technology, particularly molecular marker analysis, seed testing is becoming more precise and efficient. Continued investment in seed testing infrastructure and research is essential for sustaining a healthy and productive agricultural sector in India, especially in the face of climate change and evolving pest and disease pressures.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.