Steps in Plant Breeding: From Selection to New Variety

Plant breeding is the science of developing new crop varieties that yield more, resist diseases and pests, and suit local soils and climates. For thousands of years farmers selected the best plants by eye; modern plant breeding does the same job systematically, using knowledge of genetics to combine desirable traits from different plants into one superior variety.

Plant breeding matters because the world's food supply depends on it. The high-yielding wheat and rice varieties of the Green Revolution — shorter, sturdier plants that responded well to fertiliser — multiplied India's grain production and helped the country move toward food security. Every new variety in a farmer's field is the product of a breeding programme that typically takes 8 to 12 years.

Key Concepts

• Variety (cultivar): a group of plants selected for uniform, desirable traits, such as high yield or disease resistance, that breed true generation after generation.
• Germplasm: the collection of seeds, plants and wild relatives that breeders use as raw material — the wider the germplasm, the more traits available.
• Genetic variability: differences between plants in traits like height, grain size and disease resistance; without variability, no improvement is possible.

How It Works

1. Collection of variability: breeders gather germplasm — cultivated varieties, wild relatives and old landraces — from gene banks and diverse regions.
2. Evaluation and selection of parents: the collected material is grown and tested so the best parents for traits like yield, quality or resistance can be identified.
3. Hybridisation: the chosen parents are crossed; in flowers with both sexes, one parent is emasculated (anthers removed) and the flower is bagged to prevent unwanted pollination.
4. Selection and testing of superior recombinants: among thousands of offspring, only plants combining the desired traits are selected and self-pollinated for several generations to make them uniform.
5. Testing, release and commercialisation: the best lines are tested in multi-location field trials for 3 or more years; successful ones are officially released as new varieties.

Worked Example

Suppose a traditional wheat variety yields 3.0 tonnes per hectare, and a new bred variety yields 4.5 tonnes per hectare under the same conditions. What is the percentage gain?

1. Absolute gain: 4.5 − 3.0 = 1.5 tonnes per hectare.
2. Percentage gain: (1.5 ÷ 3.0) × 100 = 50 percent.
3. On a 10-hectare farm: extra grain = 10 × 1.5 = 15 tonnes per season.

The new variety gives 50 percent more grain — an extra 15 tonnes on a 10-hectare farm. This is why farmers adopt improved varieties so quickly once they are proven in local trials.

Common Misconceptions

• Seeds of hybrid varieties can be replanted with the same results. Wrong — the next generation segregates and loses uniformity and vigour, so farmers must buy fresh hybrid seed each season.
• Plant breeding is the same as genetic engineering. Wrong — conventional breeding crosses whole plants and selects offspring; genetic engineering inserts specific genes in the laboratory.

Real-World Applications

• Green Revolution varieties: semi-dwarf wheat (like Sonora 64) and rice (like IR-8) that doubled and tripled yields across India in the 1960s and 70s.
• ICAR institutes: India's agricultural research network that breeds, tests and releases new varieties for every major crop and region.
• Seed certification agencies: ensure the seed farmers buy is genetically pure and free of weed seeds and diseases.

Plant breeding follows a clear path: collect diverse germplasm, choose the best parents, cross them, select the finest offspring, test them across locations, and release certified seed. Taking 8 to 12 years per variety, it is slow work — but each successful variety, like the Green Revolution wheats, can feed millions more people from the same land.