Plant Breeding – Steps & Their Methods

Have you heard of hybrid tomatoes or hybrid brinjals? Have you seen different coloured maize? We all have come across these kinds of varieties in our daily diet. These are because of Plant Breeding, and these breeding techniques have now become more advanced, and they are helping to change the genetic makeup of such plants and crops to increase their yield and improve their quality and shelf life. This article covers the different steps that are involved in Plant Breeding, types of Plant Breeding and much more. Scroll down the article to know more about Plant Breeding.

What is Plant Breeding?

Plant breeding is the science of changing the traits of plant species to create desirable plant types that adapt to human needs more efficiently. It has been used to improve the quality of nutrition in products for humans and animals.

Fig: Plant Breeding

It is an essential prerequisite in the field of plant biotechnology. Plant biotechnology is a set of techniques or methods used to adapt plants for intentional usage and benefits. The interests of adopting plant breeding are as follows:
1. Improved quality
2. Increased yield of the crop
3. Longer storage period for the harvested crop
4. Development of resistance to insecticides and pesticides 
5. Improved tolerance for environmental stress like a flood, drought, etc.
All these characteristic features will result in greater production of a variety of plants and eventually plant products that are essential for the human race to survive directly or indirectly.

What are the Steps of Plant Breeding?

The steps in Plant Breeding are as follows:
1. Collection of Variability
a. Plant breeding techniques require a large variety of plants and also collection or selection of higher-yielding species. 
b. Different wild varieties of species and their wild types are a prerequisite for effective exploitation. 
c. The germplasm method is the entire collection of all the diverse alleles for all the genes in a population.
d. This collection of variability enables the breeder with a large variety to choose for the superior parents. For successful plant breed development, higher-quality varieties are required.

2. Evaluation and Selection of Parents
a. For plant breeding, the selection of high-yielding varieties and their selling creates pure lines. The pure lines mean these are the progeny of self-pollinated homozygous plants that are breeding true for that particular trait.
b. In this, better quality and better yielding parents will give rise to enhance quality offspring.

3. Hybridization or Crossing
a. In this step, the parents are cross hybridized to develop pure lines of progenies.
b. To get a high-yielding hybrid, it is important to combine high-yielding breeds. The crossing process is time-consuming and difficult to perform.
c. In this process, the emasculation of the anthers from plant variety chosen to be a male parent and pollen grains from it is placed on the stigma of plant variety chosen to be the female parent.

4. Selection and Testing of Superior Recombinants
a. In this process, all the obtained hybrids are not having all the desirable qualities. Therefore, among the progeny, plants with desirable characteristics are selected. Hence, the selection process is important to the success of the breeding objective and requires proper scientific assessment of the progeny.
b. As a result of this, this step yields plants that are superior to both parents. These plants undergo self-pollination for several generations till they reach a state of homozygosity and hence, the characters will not segregate in the progeny.

Fig: Selection and Testing Process

5. Testing and Release of Hybrids
a. The new hybrids are grown in a research lab and are tested, where their recording, performance under ideal fertilizer use, irrigation, and other crop management practices are noted down.
b. Also, in addition to this, testing of materials in farmer’s agricultural fields follows the evaluation in research fields for at least three growing seasons at several places in the country, representing all the agroclimatic zones where the crop is usually grown.
c. Same way, preservation and storage of viable hybrid seeds is a usual practice so that better yielding characters are taken away in the future.

Fig: Testing and Release of Hybrid

Methods of Plant Breeding

Plant Breeding involves different types or methods that are as follows:

1. Hybrid Breeding

In this hybrid breeding process, the two different selected breeds are crossed over to produce offspring that are more efficient and productive than the parent plants.

2. Backcrossing

a. Backcrossing is the plant breeding method most widely used to incorporate one or a few genes into an elite or adapted variety.
b. Backcross breeding is used to incorporate simply inherited traits from unadapted donor parents into recipient lines and involves repeated cycles of crossing to the recipient line (recurrent parent), followed by a selection of the trait being transferred.

3. Inbreeding

a. In this method, depending on specific species, some plants may be fertilized by themselves, i.e., known as self-fertilization. 
b. This is done to get a progeny that is exactly the same generation after generation, and by this method, it helps in preserving the original traits.
c. It is useful in three different ways – for research, as new, true-breeding cultivars, and as the parents of hybrids.
d. Inbreeding depression is one of the problems that refers to a decrease in fitness and vigour due to inbreeding, or it may be defined as the reduction or loss in vigour and fertility as a result of inbreeding.
e. Heterosis is the phenomenon in which hybrids of two homozygous inbreds (a true breeding line obtained by continuous inbreeding) of genetically, unlike constituents, are crossed together. The resulting hybrids obtained from the crossed seeds are usually robust, vigorous, and has superior characters to either of the parents.

4. Mutation Breeding

a. Naturally occurring genetic mutations are seen in many organisms like plants, animals, etc. If these types of random examples are found and seen as an improvement, then, they can be used to create new plant varieties.
b. Alternatively, mutations can be artificially encouraged or induced in plants by exposure to radiation or chemicals.

5. Molecular Marker-Assisted Selection

a. This method uses classical inbreeding or backcrossing and hybridization techniques, with a very important difference.
b. Instead of choosing desirable plants based on the way they appear or grow, breeders select plants after confirming the information on the genes the plants inherited from their parents. This is somewhat guessing and hence, the researchers should confirm the gene that is present, not just assume it is before they move forward with breeding the plant.

6. Genetic Engineering

a. Genetic Engineering is the modern process of using recombinant DNA technology to alter the genetic makeup of an organism.
b. In plant breeding, modern genetic techniques can insert desirable traits into plants.
c. The resulting plants are known as transgenic plants or genetically modified organisms (GMOs).

7. Polyploidy Breeding

a. Most of the plants are diploid in nature. Plants with three or more complete sets of chromosomes are usually common and are referred to or known as polyploids.
b. The increase of chromosome sets per cell can be artificially induced by using the chemical colchicine, which leads to a doubling of the chromosome number.
c. Generally, the main effect of polyploidy is an increase in size and genetic variability.
d. Polyploid plants often have lower fertility and grow more slowly.

8. Gene Editing

a. Gene editing or genome editing allows breeding objectives to be achieved more quickly and precisely than ever before, thereby expanding the genetic variation of a wider variety of crops.
b. This ensures high yield, develops resistance in plants against pests, high-quality seeds, and other agricultural products, etc. Usually, it targets very specific plant characteristics with razor-like precision.

9. Somatic Hybridization

a. The fused protoplast is grown in vitro with the aim to obtain a hybrid plant. So the in vitro fusion of plant protoplasts derived either from somatic cells of the same plant or from two genetically different plants is called somatic hybridization.
b. Sometimes the proto­plasts from vegetative cells and gametic cells are fused and such fusion is called somato-gametic hybridization.

Significance of Plant Breeding

Some of the significance of plant breeding are as follows:

1. The population size selected is variable and can be small or large, depending on the objective.
2. It is applicable to improving traits of low heritability because the selection is based on progeny performance.
3. In pure line selection, only the best pure line is selected for maximum genetic advantage.
4. Development of improved high-yielding varieties of vegetables and seed crops.
5. Consumes less time for the breeder.
6. Methods of Plant breeding help in developing the agricultural and rural sectors.
7. To release healthy and affordable products to the market.
8. Development of varieties that are desirable for mechanical threshing and cultivation.
9. Quality Improvement in oilseeds and vegetables.
10. Use of transgenic plants as a medicine.
11. Crops like Jatropha and Euphorbia are used for biofuel production.
12. Breeding for fibers such as cotton provides clothes for the human population.
13. Production of plant varieties with resistance to diseases, insects, frost, pests, wind, drought, acidity, and soil salinity.

Fig: Significance of Plant Breeding

Summary

Plant or crop breeding is a rapidly growing science. It is now able to make use of genetic and biotechnological innovations to efficiently develop better crop varieties. Recent biotechnological developments are helping breeders to make desired genetic changes with much greater precision. In addition, crop breeders gather a lot of information about the unique qualities of each plant. Through this article, we can conclude that science is advancing and making agricultural techniques easy for our farmers and also helping in getting high yield crops with lots of varieties for the people.

FAQs

Q.1. What are the methods of plant breeding?
Ans: The different methods of plant breeding are as follows:
1. Hybrid Breeding
2. Gene Editing
3. Polyploidy Breeding
4. Genetic Engineering
5. Molecular marker-assisted selection
6. Mutation Breeding
7. Inbreeding

Q.2. What is the purpose of plant breeding?
Ans: Plant breeding is one of the branches of agriculture that contributes positively toward, the efficiency of modern agriculture by increasing crop production, improving seed quality, and innovating methods to make crops more resistant to biotic and abiotic stresses.

Q.3. Who is the father of plant breeding?
Ans: Gregor Mendel is considered the father of plant breeding.

Q.4. What are the disadvantages of plant breeding?
Ans: Many domestic animals and plants are the results of centuries of selective breeding. Disadvantages include a reduction in genetic diversity and discomfort for animals that have very exaggerated characteristics.

Q.5. How is mutation breeding done?
Ans: Mutation breeding, sometimes referred to as “variation breeding“, is the process of exposing seeds to chemicals or radiation in order to generate mutants with desirable traits.

We hope this detailed article on Plant Breeding helps you in your preparation. If you get stuck do let us know in the comments section below and we will get back to you at the earliest.