Maintenance of Genetic Purity During Seed Production
Genetic purity refers to the degree to which a seed lot maintains its original genetic characteristics without contamination, mutation, or deterioration. Maintaining genetic purity during seed production is essential for ensuring high-yielding, disease-resistant, and high-quality crops. The genetic integrity of a variety is preserved through a systematic approach in seed production, processing, and storage.
Methods to Maintain Genetic Purity in Seed Production
Breeder Seed Production and Maintenance
- The initial step in seed production is breeder seed production, which serves as the source for foundation and certified seeds.
- It is produced under strict supervision of plant breeders in research institutions or seed agencies.
- Roguing (removal of off-type plants) is done at different growth stages to maintain purity.
Isolation Distance
- Why It’s Important: Prevents genetic contamination due to cross-pollination from other varieties or related species.
- How It’s Maintained:
- Different crops require different isolation distances based on their mode of pollination.
- Self-pollinated crops (e.g., wheat, rice) need shorter distances (3-50 meters).
- Cross-pollinated crops (e.g., maize, sunflower) require longer distances (200-400 meters).
- Wind- and insect-pollinated crops (e.g., sorghum, bajra) require the highest isolation.
- If isolation distance cannot be maintained, barrier crops (e.g., tall-growing plants like maize or sugarcane) can be used to reduce cross-pollination.
Roguing (Removal of Off-Type Plants)
- Why It’s Important: Removes undesirable plants that have mutations, contamination, or genetic variation.
- How It’s Done:
- Conducted at all critical crop growth stages—vegetative, flowering, fruiting, and maturity.
- Removal of plants that differ in height, leaf shape, color, flowering time, or disease susceptibility.
- This process ensures that only genetically pure plants remain for seed production.
Use of Genetically Pure Seed for Multiplication
- Why It’s Important: Maintaining purity at every stage of multiplication prevents accumulation of genetic deterioration.
- How It’s Done:
- Only breeder or foundation seeds should be used to produce subsequent generations.
- Avoid mixing different seed generations (e.g., breeder seed with certified seed).
- Keep proper seed production records to trace seed origin and purity.
Strict Field Inspection and Certification
- Why It’s Important: Ensures adherence to seed production standards and genetic purity norms.
- How It’s Done:
- Certification agencies conduct periodic field inspections during the growing season.
- Inspectors check for off-type plants, isolation maintenance, and disease incidence.
- Only fields meeting purity standards are approved for further seed processing.
Controlled Pollination Techniques
- Why It’s Important: Prevents unintended pollen transfer in hybrid seed production.
- How It’s Done:
- Bagging and Emasculation: Removing male parts (anthers) in self-incompatible plants and covering flowers to prevent external pollination.
- Hand Pollination: Manually transferring pollen from selected male to female flowers.
- Male Sterility Systems: Using genetically male-sterile plants to ensure controlled hybridization.
Proper Seed Harvesting and Processing
- Why It’s Important: Prevents seed mixture due to improper handling.
- How It’s Done:
- Clean harvesting, threshing, and processing equipment to avoid contamination with other varieties.
- Avoid mechanical mixing during seed drying, packaging, and transportation.
- Store different varieties in separate labeled containers.
Proper Seed Storage and Handling
- Why It’s Important: Preserves seed viability and prevents genetic deterioration.
- How It’s Done:
- Maintain low temperature (10-15°C) and humidity (<12%) to prevent fungal infections and loss of vigor.
- Use moisture-proof, airtight storage containers to prevent deterioration.
- Keep records of seed lots to track their genetic history and avoid accidental mixing.
