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Plant Breeding

Breeding Experiments
Increase in population has forced us to carry out continuous scientific experiments for the following reasons viz.

1. To develop more food crops,

2. To increase quality in food crops and

3. To have sustainable food quality in food crops and assured food supply.

By introducing specialized technology, plant breeders are now able to develop more crops, which they multiply and supply to the growers, improvement in the genetic make up of plants is called plant breeding.


Major aspects of plant breeding include

1. Creation of useful variation in the cultivable crops.

2. Selection of better crops.

3. Conducting / carrying out breeding experiments to assess the quality of the crop and

4. Release of a variety after their extensive multiplication.

Aims of Plant Breeding

The first and foremost aim in plant breeding is to create useful variation in the crop plant. This can be achieved by the following measures:

1. Bringing wild food crops to cultivation, (wheat, oats and many cereal crops were once wild plants which had been domesticated).

2. Obtaining genes from desirable plants or related species (e.g. as seeds from various parts of the world).

3. Introduction of plants from nearby regions or even from other countries for improvement of the crop. (e.g. cauliflower, tomato, potato and soyabeans).

4. By employing certain plant breeding techniques, new varieties are developed, e.g. maize, sorghum, cotton and sunflower.

5. Auto and Allopolyploid breeding.

6. By inducing mutations using physical and chemical mutagens.

7. Production of haploids by the application of plant tissue culture of anther and ovary.

8. Improvement of nutritional quality by genetic engineering (e.g. Fortified rice - iron-rich rice and carotene-rich rice).

9. Development of disease, drought and environmental stress resistant

Aspects of Plant Breeding

Pathogens like viruses, bacteria, fungi and nematodes cause many diseases in plants.  A pathogen is an organism that causes disease in another organism (the host). The development of disease in the plant depends on the following factors:

(i) host genotype

(ii) pathogen genotype

(iii) the environment

We cannot exercise a control on pathogen genotype. In fact, pathogen genotype keeps on changing with time, and is a constant problem for breeders.

Some host genotypes possess the ability to prevent a pathogen strain from producing diseases. Such host line is called resistant, and this ability is called resistance or disease resistance. The term strain has a similar meaning for pathogen as line has for the host. Those lines of a host that are not resistant to the pathogen are called susceptible. A successful breeding for disease resistance depends mainly on the following two factors:

(i) a good source of resistance

(ii) a dependable disease test

In disease test, all the plants are grown under conditions in which a susceptible plant is expected to develop disease. This allows a clear-cut identification of the disease-resistant plants, which are then selected.

Disease-resistant varieties provide the cheapest and a hazard-free means of controlling diseases. They are the only means for a predictable control of many diseases, e.g. wheat rusts, viral diseases, etc. Therefore, breeding for disease resistance is an integral part of every breeding programme. As a result, almost all modern-day varieties incorporate in them resistance for important diseases of the crop.

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