Introduction
Plant breeding is the art and science of improving crop plants to serve human needs. It focuses on developing new varieties with higher yield, better quality, resistance to pests and diseases, and adaptability to diverse environments. From early domestication of plants to modern genetic engineering and genome editing, plant breeding has played a central role in agricultural development and food security.
Historical Development of Plant Breeding
1. Ancient and Pre-Scientific Period
Human civilization began settled farming nearly 10,000 years ago. Early farmers unknowingly practiced plant breeding by selecting plants with desirable traits such as large seeds, non-shattering spikes, and better taste. This unconscious selection led to the domestication of crops like wheat, rice, maize, and potato.
2. Pre-Mendelian Scientific Era (18th – mid-19th Century)
- Joseph Kölreuter (1761–1766): First artificial hybridization in tobacco.
- Thomas Andrew Knight (1799): Hybridization studies in peas and fruit crops.
- Charles Darwin (1859): Emphasized variation and natural selection in crop evolution.
3. Mendelian Era (1900 onwards)
- Gregor Mendel (1866): Discovered laws of inheritance through pea plant experiments.
- Rediscovery of Mendel (1900): By de Vries, Correns, and Tschermak.
- Johannsen (1903): Introduced pure line theory.
- Shull (1908): Discovered heterosis (hybrid vigour).
4. Cytogenetics and Mutation Era (1910–1940s)
Knowledge of chromosomes and mutation enriched breeding. Mutagens (X-rays, chemicals) were used to create variability, while polyploidy breeding and alien gene transfers widened the scope of crop improvement.
5. Green Revolution Era (1960s–70s)
Development of semi-dwarf wheat by Norman Borlaug and M.S. Swaminathan, and high-yielding rice (IR8) by IRRI, led to a dramatic rise in food grain production. India became self-sufficient in wheat and rice.
6. Modern Biotechnological and Genomic Era
Recent advances include tissue culture, molecular markers, genetic transformation (Bt cotton, Golden Rice), genome sequencing, CRISPR-Cas9 editing, and speed breeding. These methods enable precision breeding in record time.
Concepts of Plant Breeding
- Selection: Mass selection, pure line, and clonal selection.
- Hybridization: Crossing genetically different parents (interspecific, intergeneric).
- Heterosis: Hybrid vigour utilized in maize, cotton, rice.
- Mutation Breeding: Use of mutagens for variability (Pusa Ruby tomato, Sharbati Sonora wheat).
- Polyploidy Breeding: Induced chromosome doubling (triploid banana).
- Backcross Breeding: Introgression of a specific trait into an elite variety.
- Molecular and Genomic Breeding: MAS, transgenics, genome editing.
Nature of Plant Breeding
- Scientific and systematic – Based on genetics, cytology, pathology, statistics.
- Goal-oriented – Directed to increase yield, resistance, and adaptability.
- Dynamic – Continuously evolving with new tools.
- Multidisciplinary – Involving genetics, biotechnology, agronomy, entomology.
- Art and science – Requires creativity and farmer’s practical wisdom.
Role of Plant Breeding
- Yield improvement – Higher production per unit area.
- Quality enhancement – Biofortified crops rich in protein, iron, vitamins.
- Disease and pest resistance – Wheat resistant to rusts, rice resistant to blast.
- Abiotic stress tolerance – Varieties tolerant to drought, salinity, heat.
- Sustainability – Low input, resource-efficient farming.
- Climate resilience – Crops adapted to changing environments.
Major Achievements in Plant Breeding
1. Green Revolution Crops
Semi-dwarf wheat (Kalyan Sona, Sonalika), rice varieties IR8 and IR36.
2. Hybrid Crops
Hybrid maize (USA), hybrid cotton and hybrid rice (India).
3. Disease Resistance Breeding
HD 2967 wheat (rust resistance), IR64 rice (blast resistance).
4. Mutation Breeding
Pusa Lal tomato, Sharbati Sonora wheat, improved groundnut varieties.
5. Biofortified Crops
Golden Rice (Vitamin A), Quality Protein Maize (QPM), iron-rich pearl millet.
6. Horticultural Improvements
Mango hybrids, banana Grand Naine, tomato hybrids like Pusa Hybrid-2.
Future Prospects of Plant Breeding
- Climate-smart breeding – Varieties tolerant to drought, salinity, heat, flooding.
- Nutritional security – Wider use of biofortification.
- Genomic selection – Predicting performance using genome-wide markers.
- CRISPR and gene editing – Precision breeding tools.
- Speed breeding – 6 generations of wheat in one year.
- AI and digital breeding – Data-driven decision making in breeding.
- Alien gene transfer – Using wild relatives for novel resistance genes.
Genetics in Relation to Plant Breeding
- Mendelian genetics – Basis of inheritance and segregation of traits.
- Pure line theory – Foundation of self-pollinated crop improvement.
- Heterosis – Explained through dominance and overdominance.
- Mutation – Generates new variability for breeders.
- Cytogenetics – Key for polyploidy breeding and alien gene transfer.
- Molecular genetics – DNA markers, QTL mapping, gene pyramiding.
- Population genetics – Helps in recurrent selection and population improvement.
- Epigenetics – Regulates stress tolerance and adaptability.
Conclusion
Plant breeding has been central to human survival and agricultural growth. From unconscious selection to molecular breeding and CRISPR-based genome editing, its role has expanded enormously. It not only increases yield but also ensures nutritional security, sustainability, and resilience to climate change. With continued integration of genetics, biotechnology, and artificial intelligence, plant breeding will remain the backbone of global food and nutritional security in the future.
