Plant Breeding Lecture Notes

Importance of Plants

• Plants are foundational to ecosystems, forming the bottom of the food chain as producers.
• 85% of human food consumption is plant-based.
• Plants grown for food are termed food crops.
• Food crops are heavily dependent on water, soil, and climate.
• Environmental conditions like drought can lead to food shortages or famine, such as the Great Bengal famine in 1943.
• Increasing population necessitates increased food production.

Plant Breeding Overview

• Plant breeding aims to improve crop quality and productivity.
• Defines plant breeding as the science of changing genetic traits for better cultivation and resistance.
• Breeding involves crossbreeding plant varieties to create desired traits.
• Desirable traits include increased yield, quality, environmental tolerance, disease resistance, and pest tolerance.

Hybridization

• Process of breeding genetically different but related individuals to produce hybrids.
• Notable contributors include Gregor Mendel and Charles Darwin.

Steps in Plant Breeding

Step 1: Collection of Variability

• Genetic variation is crucial for breeding.
• International efforts are made to collect plant varieties globally (germ plasm collection).
• Germ plasm collections exist in India at ICRISAT, Hyderabad and NBPGR, New Delhi.

Step 2: Evaluation and Selection of Parents

• Initial collections were based on visible traits, but environmental conditions can mislead.
• Plants are grown under controlled conditions for evaluation.
• Pure homozygous plants are selected for further breeding.

Step 3: Cross Hybridization Among Selected Parents

• Cross hybridization creates hybrid progeny with desired traits.
• Artificial hybridization involves controlled pollination and several steps:
  • Selection: Choose parents with desired traits.
  • Emasculation: Remove male parts to prevent self-pollination.
  • Bagging & Tagging: Prevent contamination; provide plant information.
  • Pollination: Dust stigma with pollen from selected plants.
  • Tagging: Record relevant information like date and parent details.

Step 4: Selection & Testing of Superior Recombinants

• Hybrids are tested and self-pollinated over generations to achieve uniformity.
• Pure lines (cultivars) are evaluated under ideal conditions and compared to existing cultivars.

Step 5: Multiplication of Improved Seed

• Approved cultivars are grown to multiply seeds.
• Seeds are tested and certified by National Seed Corporation (NSC).
• Certified seeds are distributed to farmers.

Limitations of Cross Hybridization

• Time-consuming and tedious.
• Desired traits may not combine as planned.
• Only a small percentage of crosses produce desired outcomes.

Conclusion

• Plant breeding is essential for improving food availability and managing limited agricultural land.