What is plant breeding and what are the techniques?

Introduction

Breeding is the way of producing offspring through sexual reproduction. However, plant breeding is a biotechnological process that occurs with the intervention of humans. The primary motive of plant breeding is to produce crops with better quality and quantity.  

The continuous growth of the population made scientists think about alternate ways of quality food production. Another such challenge is the season of production. Most of the crops have a particular season of reproduction and fruit formation. Due to urbanization, the amount of agricultural land is also decreasing.

Plant breeding technique becomes an ideal solution for these problems. Being a mostly laboratory-based method, it requires less land. The amount of production is also higher than the traditional method. Production is year-long. 

Fundamentals of plant breeding

Plant breeding is a biotechnological strategy where two plants with desirable qualities are taken to create a plant with superior quality. Two plants with higher qualities are crossed with each other so that the offspring can express both characteristics.

Though the modern concept of plant breeding arose after Mendel’s experiments, history has evidence of the same 10000 years back.

Mendel proved that the characteristics of parents are inherited in offspring independently. This discovery gave the scientists the idea that if two plants with superior quality are crossed, then the offspring with have both characteristics as dominant.

Objectives of plant breedings

  • To produce plants with the characters according to the need.
  • To increase the quantity of the crop.
  • To develop disease-resistant plants.
  • To produce plants tolerant to stress.¬†

Traditional breeding methods

Traditional plant breeding methods have primarily two steps. These are

  • Selection
  • Hybridization

Selection

The first step in traditional breeding is selecting a plant or plants having desirable characteristics. This is called selection. In traditional breeding, farmers often choose a group of plants showing the needed character.

 Hybridization

Hybridization is the process that involves cross-fertilization. When two parents with different characters are crossed with each other to produce offspring, it is known as hybridization. The offspring is called a hybrid. (1)

Modern techniques

Modern plant breeding is mostly based on molecular biology. Two such modern techniques are-

  • Marker-assisted breeding
  • Genetic engineering

Marker-assisted breeding

Sometimes more than one gene can express the desirable character. This is a method that uses a molecular marker (a particular DNA sequence at a certain location within the genome) to determine the very gene responsible for the desirable character.

The molecular markers can locate various genes and analyze their functions. Then, according to the need, that particular gene is extracted and transferred to the crop.

Genetic engineering

Genetic engineering is a biotechnological process where the gene sequences are altered. After molecular markers identify the gene sequence, restriction endonuclease is used to cut. Then it is inserted into a vector (genetic materials of various microorganisms that carry DNA sequence).

The vector is then injected into the crop. The desired DNA sequence enters the plant along with the vector. Then expresses itself. (2)

Steps in Plant breeding

The steps of plant breeding are

  • Collection of Variables
  • Selection
  • Hybridization
  • Evaluation
  • Seed multiplication and distribution among farmers

Collection of Variables

The first phase entails gathering germplasm, which is a collection of plants or seeds representing all potential alleles for every gene in a particular crop. Even wild variations and farmed species relatives are included in this collection.

Selection

In this step, plants with desirable characters are selected. The desirable characteristics of both parents are found in offspring.

For example, if a breeder wants to develop a better yielding, disease-resistant variety, he will cross one having high yielding and another having disease-resistant capability.

Selection is mainly two types. These are-

  • Mass selection
  • Pureline selection

Mass selection

In mass selection, numerous plants with various desired phenotypes are chosen, and the seeds from these plants are combined to create a new variety. The plants are chosen based on their phenotype, or outward appearance. Compared to the initial population, the population created from the chosen plants would be more uniform.

Pureline selection

A pure line is any breed of an organism that has undergone repeated self-fertilization and has achieved homozygosity for a certain feature. If the organism is bred with another true breeding organism, the trait is passed on to offspring.

Hybridization

Hybridization is the procedure of crossing between two parents with different characters. The offspring will have both of their characteristics.

The traditional method of transferring pollen from one plant to the stigma of another is used in this laborious and time-consuming procedure. Despite the effort put forward, just one or two of every few hundred offspring exhibit the optimal combination of traits.

Evaluation

After evaluating the developed offspring, those who possess the appropriate mix of traits are self-pollinated to achieve homozygosity.

Seed multiplication and distribution among farmer

The new lines are cultivated in testing plots where their agronomic characteristics, such as quality, yield, disease resistance, etc., are examined. Then the crops are made available for commercial sale to the general population after successful testing. (3)

Importance of Plant Breeding in Genetic Diversity

In breeding two parents with different characters are crossed with each other. When they produce offspring, they both pass their genes to it. Hence, offspring bears both of their traits.

This helps to form a new variety, sometimes even a new species. This helps in increasing diversity. Even if, a new variety is not formed, changes definitely occur in gene pools. So, genetic diversity occurs.

Impact of Plant Breeding in Germplasm Conservation

Conserving the gene sequences of endangered and economically valuable species is the motive of germplasm conservation. Using plant breeding methods helps this process in many ways.

  • The whole organism or plant does not need to be conserved.
  • It can make multiple copies of gene sequences at a time. So, a large number of new crops can be produced.
  • Genetic alternation can make the crops more resistant to environmental hazards. (4)

Plant breeding and agricultural challenges

Some plants with inherent capability to resist pathogens and pests. Few genes are responsible for their qualities. Plant breeding enables the potion of transferring that particular gene in a crop to develop that quality.

Yellow mosaic virus-resistant genes were present in a wild variety of Abelmoschus esculentus (Okra). A new variety Prabhani Kranti was produced by transferring those in the normal okra variety.

In similar ways, many drought-resistant varieties were produced. Plant breeding helps to develop resilient characters like these in crops.

Breeding and enhancement of nutrition

Another use of plant breeding is enhancing the nutritional profile of crops. Using breeding methods, nutrients like vitamins and minerals can be inserted or their amount can be enhanced. In Golden rice, vitamin A is inserted through plant breeding.

Breeding and environmental sustainability

Environmental sustainability is the capacity to preserve natural resources for the benefit of both the present and future generations while preserving the ecological balance of our planet.

If breeders can integrate new genes through breeding, this will enhance genetic diversity. Diversified plants can withstand environmental challenges like drought, excessive heat, rain, climate changes, etc. The chances of extinction will be less. 

Ethical and social consideration of plant breeding

The ethical aspect of plant breeding deals with the impact of the changes. The changes or introduction of new characters should always be beneficial for society. For example, if a breeder is considering developing a higher-yielding variety, he will have to ensure that quality is not compromised. 

No such side effect can result due to alteration of genes. Earlier, we have witnessed that often genetically modified crops had different side effects. 

Success stories of plant breeding and future directions

One of the biggest success stories of plant breeding is the production of Triticale. Triticale is a hybrid of wheat (Triticum aestivum) and rye (Secale cereale). The commercial version of Triticale is disease-resistant with higher environmental tolerance, better yield, and greater quality.

Another one is Golden rice, where vitamin A was inserted in rice. Wheat varieties like Sonara, Kalyansona are the results of plant breeding. 

Q&A

1. What are the types of plant breeding?

The types of plant breeding are

  • Inbreeding
  • Backcrossing
  • Hybrid breeding
  • Genetic engineering
  • Molecular marker-assisted breeding

2. What is the difference between plant breeding and hybridization?

Hybridization is part of plant breeding. Plant breeding is a process to introduce new character traits in plants. 

At one step of plant breeding, two plants, one male and one female are crossed with each other to produce offspring with both character traits. This offspring is called hybrid and the process is called hybridisation.

3. What is plant breeding in genetics?

Plant breeding is a biotechnical process where two plants with different characteristics or genetic makeup are crossed with each other and produce an offspring that bears both of their characteristics.

4. What is the process of breeding?

Breeding is the process of producing offspring through sexual reproduction. In this process, two parents with different characters are crossed with each other so that offspring can express the characters of both parents.

Summary

  • Plant breeding is the method to introduce new character traits in plants.
  • Two parents with different characters are crossed with each other.
  • Traditionally, plants with desirable characteristics are selected and then a hybrid is formed.
  • With progress in biotechnology, genetic alteration is often performed.
  • Breeders use a molecular marker to identify the responsible gene for the desired character and extract the gene using restriction endonuclease. Then insert in another crop.
  • Plant breeding is useful to produce varieties that are higher-yielding, disease-resistant, and resilient to environmental conditions.
  • Production of Triticale and Golden rice is proof of successful plant breeding programs.

Written By: Pritha Chowdhury