Introduction
Seed testing is the scientific evaluation of seed quality attributes—including viability, purity, moisture, and seed health—to determine its suitability for sowing, marketing, and long-term storage. Conducted in accordance with International Seed Testing Association (ISTA) standards, seed testing serves as the cornerstone of quality control in certified seed production programs.
Key Methods of Seed Testing
Standard seed testing protocols evaluate distinct physical, physiological, and pathological parameters using certified laboratory and field techniques:
- Physical Purity Test: Evaluates the physical composition of a seed lot by separating the working sample into pure seeds, other crop seeds, weed seeds, and inert matter. The purity percentage is determined by weight:
Purity (%) = (Weight of pure seed / Total weight of working sample) × 100. - Moisture Content Test: Essential for determining seed storability and safe drying thresholds. It is predominantly evaluated using the Hot Air Oven method (constant temperature drying). On a wet basis, moisture content is calculated as:
Moisture (%) = [(W1 - W2) / W1] × 100 (where W1 is the initial sample weight and W2 is the oven-dry sample weight). - Germination Test: Evaluates the physiological capacity of a seed lot to produce normal seedlings under optimal laboratory conditions. Substrata commonly used include Top of Paper (TP), Between Paper (BP), or Sand. Germination is strictly measured by seed count:
Germination (%) = (Number of normally germinated seeds / Total number of seeds planted) × 100. - Seed Viability (Biochemical) Test: The Topographical Tetrazolium (TZ) Test provides a rapid determination of seed viability without waiting for complete germination. The 2,3,5-triphenyl tetrazolium chloride solution reacts with active dehydrogenase enzymes in respiring living embryo tissue, staining it carmine red through the formation of insoluble formazan.
- Genetic and Varietal Purity Test: Ascertains trueness-to-type. It is traditionally assessed via field-based Grow-Out Tests (GOT) assessing morphological markers during full plant development, supplemented by advanced laboratory techniques such as SDS-PAGE electrophoresis and DNA molecular marker assays (PCR/RAPD).
- Seed Health Test: Detects seed-borne pathogenic fungi, bacteria, viruses, and nematodes. Standard protocols include the Blotter method, Agar plate method, and seedling symptom tests.
Conclusion
Mandatory seed testing guarantees the distribution of genetically authentic, high-vigour, and disease-free seeds to farming communities. Enforcing ISTA standards and statutory provisions under the Seeds Act, 1966, safeguards crop establishment, minimizes field losses, and optimizes overall agricultural productivity.