Science > Biology > Improvement in Crop variety > Improvement in Crop Variety
The plant breeding technique is the combination of desirable and suitable characteristics from many selected crops into a single hybrid crop, then to multiply it and make the hybrid plant available to farmers for cropping. Thus Crop improvement refers to the genetic alteration of plants to satisfy human needs. The branch of applied biology concerned with the improvement of crop varieties is called plant breeding.
Need for Improvement in Crop Variety:
- Continuous increase in human and animal population has created a demand to increase food and fodder production.
- There is a rise in the standard of living and people have become more conscious about their health. There is a competition in the market due to the demand for quality products.
- It becomes necessary to increase the crop variety to produce disease-resistance offspring of the crops.
- It is helpful in developing superior varieties in terms of quantity and quality of yield.
Plant Breeding:
Plant breeding is a technique (purposeful manipulation) of improvement of economically important crop plants and production of a new crop that are better suited for the cultivation, give better yield and the disease resistance. Conventional plant breeding is in practice from 9,000-11,000 years ago. Most of our major food crops are derived from the domesticated varieties in ancient times.
Classical plant breeding involves crossing or hybridization of pure lines having desired characters, followed by artificial selection to produce plants with desirable traits of higher yield, nutrition, and resistance to diseases. With advancements in genetics, molecular biology, and tissue culture, plant breeding is now increasingly being carried out by using molecular genetic tools.
Objectives of Plant Breeding:
Increased yield:
The productivity of the crop per unit acre of land is the criteria of the measurement of the yield. Majority of plant breeding programs aims at increased yield. This is achieved by developing more efficient genotypes. Through artificial selection, cross-breeding and hybridization, high yielding varieties (HYV) are developed. These varieties improve productivity per acre of the land.
Improved Quality:
By plant breeding, a crop variety of improved nutritional values, taste and shelf life can be developed. Shakti, Rattan, and Protina are the three varieties of maize developed and released for cultivation. e.g. pulses are selected for better protein quality, oil seeds for higher quantity and quality of oil, wheat for baking quality, fruits for better taste and vegetables/fruits for longer shelf life
Crops are cultivated with qualities which are peculiar to a particular crop
- Rice: milling, cooking quality, aroma, and grain colour
- Wheat: milling and baking quality and gluten content.
- Pulses: Protein content and improving sulphur containing amino acids
- Oilseeds: PUFA content
Elimination of Toxic Substance:
By plant breeding, toxic substances from plants are removed in a new variety. HCN content in jowar plants, Erucic acid in Brassicas, Cucurbitacin in cucurbits is removed by plant breeding.
Developing Resistance against biotic and abiotic stresses:
- Biotic stress: Pests are insects and molluscs which feed on plants and destroy them. Wild varieties of plants are found to have a good pest, parasite, and disease resistant. Genes of such plants are used to develop the disease-resistant high yielding plant.
- Abiotic stress: New varieties of crops are capable of surviving in environmental changes like drought, waterlogging, the salinity of soil, heat, cold, frost, etc.
Change in Maturity Duration:
The shorter the duration of crop variety from its sowing to harvesting, the more economical is the variety. By plant breeding, new varieties of early maturing varieties of crops are developed. It increases the yield and productivity of land per acre. It helps farmers to raise multiple crops in a year over the same piece of land. These new varieties are uniform in maturation hence harvesting becomes easy. Losses are reduced during harvesting.
Wider Adaptability:
New varieties which are insensitive to temperature and light should be developed. It allows the crops to be grown under different climatic conditions in different areas throughout the year.
Desirable Agronomic Traits:
To achieve higher productivity, new varieties should have desirable agronomic characters. It increases productivity, for example, tallness and profuse branching are desirable characters for fodder crops; while dwarfness and short maturation are desired in cereals so that less nutrients are consumed by these crops.
Other Objectives:
Other objectives include improved agronomic characters, reducing the plant height to prevent lodging, photo-insensitivity, Non-shattering nature of grain and grams, synchronized maturity, elimination or introduction of dormancy.
Steps in Plant Breeding:
New varieties of plants can be developed by introducing variations or differences in the genetic composition of the existing varieties and then selecting the varieties with desired character or characters. The process involves the following steps.
Collection of Germplasm:
The entire collection (of plants/seeds) having all the diverse alleles for all genes in a particular crop is called germplasm collection.
Selection and Testing Superior Recombinants:
The selection from the germplasm collection involves picking up the better one from the entire crop plants. The collected germ-plasm is now evaluated to identify the plants showing the desirable combination of characters.
Introduction of Genetic Variations:
Selected plants in the first step are used in the process of hybridization. Hybridization is the technique introducing characters of two desirable species into single offsprings by artificial pollination to create a new genetic combination.
Evaluation, Release, and Commercialization of New Cultivar Varieties:
The newly developed hybrid varieties of plants are cultivated in research fields and evaluated for yield, quality, nutritional content, taste, colour and for disease resistance. They are cultivated under monitored conditions with ideal fertilizer applications, irrigation, and other management practices. For the next three seasons, they are developed and tested in fields in different locations. Then after successful cultivation, they are notified for release for commercial cultivation.
Multiplication of Improved Seeds and Their Release to Farmers:
Seeds developed in the above step are multiplied and after certification is packed and sealed and distributed to farmers.
These steps are explained in details in the next articles.
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