Breeding is the branch of biology which deals with the production of improved and new crop varieties, which are superior to exisiting varieties with several charactceristics. It helps for the production of several superior qualities originally found in verious plants crops into a single plant.
Plant breeding is the branch of biology that deals with improvement of heredity characters of crops and production of new crops with better and varieties of characters.
Mutations are defined as the sudden heritable variation in plants which is occur due to the arrangement of genes, change in size and structure of chromosome, change in number of chromosome and change in the body. All the types of heredity changes in genotypes of plant are included in mutations. Different changes or improvement of verities are occurring due to the mutation.
Whenever the two inbred homozygous parents are crossed, as a result the heterozygous hybrid produced which are more advance and superior than their parents. Heterosis is defined as the superiority of hybrids over their parents. These sorts of hybrids may have improved in general fitness, resistant to different diseases, more adaptability to the environment and shows best in quality and quantity both. These sorts of development observed in generation are also known as hybrid vigour. In 1914, Shull was the first person to coined the term ‘heterosis’ for hybrid vigour.
Nepal is agrobased country; most of the people are depended on the agriculture. About 95% of total populations of Nepal are depending on the agriculture. About 2.3 million hectares of land is used for cultivation which is about 16.49 percent of the total land area. In Nepal agriculture production food grain are predominant. Main food grains grown in Nepal are rice, maize, millet, barley and wheat. About 90% of total supply is food grain. Mostly produced food grains are rice about 61%, maize-25%, wheat-9%, millet-4% and barley-2.6% per year. The main food crops grown in terai region are rice and wheat. Main food crops grown in hilly region are maize, barley and millet. In Himalayan region buckwheat is grown mostly.
The population growth rate of Nepal is 2.2-2.6% per but the growth rate of food grain production is very low, it is about 1.2% annually. The challenging problems of the present situation of Nepal is that population is increasing day by day whereas the food grain production is decreasing. If the condition goes like this Nepal will face the problem of food shortage. There are many problems for the decrease in the production of food grain. One of the problems is that plants or crops are attacked by different diseases which are caused due to different insects, virus, fungi, etc. Following two methods can control the problems of different diseases:
1. Application of biopesticides: Biopesticides are defined as the chemical substance which help to destroy and eradicate the different harmful insects, bacteria, virus, fungi, etc which causes different diseases to the crops
2. Raising of resistant varieties: Though the use of different biopesticides, herbicides and bioinsecticides help to eradicate the different insects, virus, bacteria, fungi, etc. it is not environmentally safe. Instead of using them it is better to grow diseases resistant varieties which can the most useful method to control and eradicate pathpgens.
In contest of Nepal also various diseases resistant varieties are produced by different research center or farms by the breeding technique, mutations, grafting and tissue culture. Some of the diseases resistant varieties are described below:
Terai region- In terai region mansuli, IR-20, CH-45 and IR-8 are grown.
Hilly region- In hilly region Taichung-176 and chainug-242 are grown.
Plant tissue culture is the art of science to grow new plant with the help of different parts of plants. A small part of the plant can produce the whole plant. Plants are totipotency in nature which means that every part have capacity to grow in new plant. Many diseases resistant and high yielding plant are developed by the tissue culture technique. Some of them are listed below:
Types of virus eliminated
Potato mosaic virus
Tobacco (Nicotiana tobacco)
Tobacco mosaic virus
Cucumber mosaic virus
Soybean mosaic virus
Table: virus resistant plants created using tissue culture
By the following method improvement of animals is brought about by selection for desirabletraits:
1.Inbreeding- It is the process in which mating is done among the closely related individuals. Many valuable breeds of different domestic animals are resulted over a period of time with the combination of inbreeding. Some of the examples are as follows:
2. Out-breeding or hybridization- It is the process which involve with the mating of two unrelated individuals. This is the technique of creating new breed. It is also known as hybrid. For examples; mule is the hybrid of mare and ass, Blue roan is the hybrid of white short horn and black Angus cattle, etc.
3. Artificial insemination- It is the process which involve with collection of better quality semen of male animals and introduce to the oviducts of female. The collected semen can be preserved in the liquid of nitrogen and also can be transported in different places.
Disadvantages of artificial insemination
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Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069
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1. Heterosis is defined as the superiority of hybrids over their parents.
2. Mostly produced food grains are rice about 61%, maize-25%, wheat-9%, millet-4% and barley-2.6% per year.
3. Rice is the crop which is grown predominantly in Nepal. Per year 122 kg rice is consumed per capita.
4. The semen of one male can be used to inseminate a number of different female.
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