💏Plant Breeding: Definition, Domestication, and Methods

Why Plant Breeding Matters

The Green Revolution that saved millions from famine was driven by plant breeding — semi-dwarf wheat varieties developed by Norman Borlaug and dwarf rice varieties like IR-8 dramatically increased yields across Asia. Today, plant breeding continues to address food security through higher yields, disease resistance, nutritional quality, and climate adaptation. Every improved crop variety on a farmer’s field is the product of systematic breeding.

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Plant Breeding

• Plant breeding can be defined as an art, a science, and technology of improving the genetic makeup of plants in relation to their economic use for the man kind. In other words, it is the systematic approach to developing new and improved crop varieties that are better suited to human needs — whether for food, fibre, fuel, or other purposes.
• Aim of Plant Breeding: Plant breeding aims to improve the characteristics of plants so that they become more desirable agronomically and economically. The specific objectives may vary greatly depending on the crop under consideration. For example, the goals for a cereal crop like wheat may focus on yield and disease resistance, while those for a fruit crop may emphasize quality and shelf life.

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Domestication

• The process of bringing a wild species under human management is referred to as domestication. This is the foundational step in agriculture — transforming wild plants into cultivated crops through sustained human effort over generations.
• Domestication may be the most basic method of plant breeding. It represents the earliest form of selection carried out by humans, long before scientific breeding methods were developed.
• Domestication continuous today and is likely to continue for some time in future. There are still many wild species with untapped potential waiting to be brought under cultivation.
• Ex: In case of timber trees medicinal plants, microbes. These organisms are still being domesticated as we discover new uses for them.
• During the long period of historic cultivation natural selection has definitely acted on the domesticated species. Over thousands of years, the combined forces of natural selection and human preference have shaped crops into their present forms.
• Movement of man from one place to another brought about the movement of his cultivated plant species. This migration of people and their crops played a major role in spreading cultivated plants across continents.

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Methods of Plant Breeding

Activities of plant breeding: Creation of Variation → Selection → Evaluation → Multiplication → Distribution ^{UPPSC 2021}

These five steps form the backbone of every breeding programme. First, genetic variation is created (through hybridization, mutation, or other means), then superior individuals are selected, their performance is evaluated across environments, and finally the best varieties are multiplied and distributed to farmers.

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Methods of Breeding Autogamous species

Plant breeding methods that are used for genetic improvement of self-pollinated or autogamous species include:

1. Plant Introduction
2. Pureline Selection
3. Mass Selection
4. Pedigree Method
5. Bulk Method
6. Single Seed Descent Method
7. Backcross Method
8. Heterosis Breeding
9. Mutation Breeding
10. Polyploidy Breeding
11. Distant Hybridization
12. Transgenic Breeding

Self-pollinated crops (like wheat, rice, peas, and tomato) are naturally homozygous, which means the breeding methods for these crops focus on isolating the best homozygous lines from existing or newly created variation.

Four breeding approaches, viz., recurrent selection, disruptive selection, diallele selective mating, and biparental mating are used for population improvement.

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Methods or Breeding Allogamous species

Breeding methods that are used for genetic improvement of cross pollinated or allogamous species include:

1. Plant introduction
2. Mass and Progeny selection
3. Backcross method
4. Heterosis breeding
5. Synthetic breeding
6. Composite breeding
7. Polyploidy breeding
8. Distant hybridization
9. Transgenic breeding

Cross-pollinated crops (like maize, bajra, and sunflower) are naturally heterozygous, and breeding methods for these crops aim to maintain or exploit this heterozygosity for vigour and yield.

Mutation breeding is rarely used in allogamous species. This is because cross-pollinated species already possess abundant genetic variability, making it unnecessary to induce additional mutations in most cases.

Three breeding approaches viz., recurrent selection, disruptive mating and biparental mating are used for population improvement.

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Methods of Breeding Asexually Propagated Species

Important breeding methods applicable to asexually propagated species are:

1. Plant Introduction
2. Clonal selection
3. Mass selection
4. Heterosis breeding
5. Mutation breeding
6. Polyploidy breeding
7. Distant hybridization
8. Transgenic breeding

Asexually propagated crops (like sugarcane, potato, and banana) maintain the exact genotype of the parent plant through vegetative propagation. This means that once a desirable genotype is identified, it can be multiplied indefinitely without any change in its genetic constitution.

Mass selection is rarely used in asexually propagated species. Since individual clones can be evaluated and maintained directly, there is little need for bulking seeds as done in mass selection.

Four breeding approaches, viz., recurrent selection, disruptive selection, diallele selective mating, and biparental mating are used for population improvement.

Explore More

• Plant Breeding Methods — Overview

Summary Cheat Sheet