Def aim-obj-scope of ci(1)

Def aim-obj-scope of ci(1)

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  1 Lecture No:1 Definition, Aim,Objectives and Scope of Plant Breeding Definition : Plant breeding can be defined as an art, a science, and technology of improving the genetic make up of plants in relation to their economic use for the man kind. or Plant breeding is the art and science of improving the heredity of plants for the benefit of mankind. or Plant breeding deals with the genetic improvement of crop plants also known as science of crop improvement. or Science of changing and improving the heredity of plants Aim: Plant breeding aims to improve the characteristics of plants so that they become more desirable agronomically and economically. The specific objectives may vary greatly depending on the crop under consideration. Objectives of Plant Breeding : 1. Higher yield : The ultimate aim of plant breeding is to improve the yield of economic produce. It may be grain yield, fodder yield, fibre yield, tuber yield, cane yield or oil yield depending upon the crop species. Improvement in yield can be achieved either by evolving high yielding varieties or hybrids. 2. Improved quality: Quality of produce is another important objective in plant breeding. The quality characters vary from crop to crop. Eg. grain size, colour, milling and backing quality in wheat. Cooking quality in rice, malting quality in barley, size, colour and size of fruits, nutritive and keeping quality in vegetables, protein content in pulses, oil content in oilseeds, fibre length, strength and fineness in cotton. 3. Abiotic resistance : Crop plants also suffer from abiotic factors such as drought, soil salinity, extreme temperatures, heat, wind, cold and frost, breeder has to develop resistant varieties for such environmental conditions. 4. Biotic resistance : Crop plants are attacked by various diseases and insects, resulting in considerable yield losses. Genetic resistance is the cheapest and the best method of minimizing such losses. Resistant varieties are developed through the use of resistant donor parents available in the gene pool. 5. Change in maturity Duration / Earliness : Earliness is the most desirable character which has several advantages. It requires less crop management period, less insecticidal sprays, permits new crop
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  2 rotations and oftenextends the crop area. Development of wheat varieties suitable for late planting has permitted rice-wheat rotation. Thus breeding for early maturing crop varieties, or varieties suitable for different dates of planting may be an important objective. Maturity has been reduced from 270 days to 170 days in cotton, from 270 days to 120 days in pigeonpea, from 360 days to 270 days in sugarcane. 6. Determinate Growth : Development of varieties with determinate growth is desirable in crops like Mung, Pigeon Pea (Cajanus cajan ), Cotton (Gossypium sp.), etc. 7. Dormancy : In some crops, seeds germinate even before harvesting in the standing crop if there are rains at the time of maturity, e.g., Greengram, Blackgram, Barley and Pea, etc. A period of dormancy has to be introduced in these crops to check loss due to germinatio n. In some other cases, however, it may be desirable to remove dormancy. 8. Desirable Agronomic Characteristics: It includes plant height, branching, tillering capacity, growth habit, erect or trailing habit etc., is often desirable. For example, dwarf ness in cereals is generally associated with lodging resistance and better fertilizer response. Tallness, high tillering and profuse branching are desirable characters in fodder crops. 9. Elimination of Toxic Substances : It is essential to develop varieties free from toxic compounds in some crops to make them safe for human consumption. For example, removal of neurotoxin in Khesari (Lathyruys sativus) which leads to paralysis of lower limbs, erucic acid from Brassica which is harmful for human health, and gossypol from the seed of cotton is necessary to make them fit for human consumption. Removal of such toxic substances would increase the nutritional value of these crops. 10. Non-shattering characteristics: The shattering of pods is serious problem in green gram. Hence resistance to shattering is an important objective in green gram. 11. Synchronous Maturity : It refers to maturity of a crop species at one time. The character is highly desirable in crops like Greengram, Cowpea, and Cotton where several pickings are required for crop harvest. 12. Photo and Thermo insensitivity: Development of varieties insensitive to light and temperature helps in crossing the cultivation boundaries of crop plants. Photo and thermo-insensitive varieties of wheat and rice has permitted their cultivation in new areas. Rice is now cultivated in Punjab, while wheat is a major rabi crop in West Bengal. 13. Wider adaptability : Adaptability refers to suitability of a variety for general cultivation over a wide range of environmental conditions. Adaptability is an important objective in plant breeding because it helps in stabilizing the crop production over regions and seasons. 14. Varieties for New Seasons : Traditionally Maize is a kharif crop. But scientists are now able to grow Maize as rabi and zaid crops. Similarly, mung is grown as a summer crop in addition to the main kharif crop.
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  3 Scope of plantbreeding Since the cultivable land is shrinking and there is no scope for increasing the area under cultivation, the only solution to meet the food requirement is by increasing the crop yield through genetic improvement of crop plants. There are two ways by which yield improvement is possible. 1. Enhancing the productivity of crops This can be done a) By the proper management of soil and crops involving suitable agronomic practices and harvesting physical resources. b) By using high potential crop varieties created by appropriate genetic manipulation of crop plants. 2. Stabilizing the productivity achieved This is done by using crop varieties that are bred especially for wide adaptation or for specific crop zones to offset the ill effects of unfavorable environmental conditions prevailing in the areas. Plant breeding, the past, present and future scopes Indian agriculture remained stagnant particularly during early days. Long spells of severe drought and serious out break of disease in some parts of the country led some futurologists to state that a possible boom in India by the end of the decade. However, we achieved break through in crops such as rice, wheat, pearlmilelt, jowar and maize. The indica x japonica cross derivative ADT 27 is the first high yielding rice of Tamil Nadu. The identification of Dee Gee Woo Gen and release of Wonder rice IR 8 (peta x DGWG) changed the scenario from poverty to problem of plenty. Like wide identification of dwarfing gene in Japanese wheat variety Norin-10 by Borlaug and breeding of Mexican dwarf wheat varieties led to the release of wheat varieties life Kalyan sona in India. In pearl millet, breeding by male sterile line Tift 23A at Tifton, Georgia by Burton and his coworker and later on its introduction to India led the release of hybrid bajra HB1 to HB4, which increased bajra production many fold. In Jowar, breeding of first male sterile line combined kafir 60A and its introduction into India led to the release of first hybrid sorghum CSH 1 (CK 60A x IS 84) during 1970s. At present we are in search of alternate source of cytoplasm in almost all crops to breed hybrids with new source of cytoplasm to prevent the possibility of appearance of new pest and diseases. Thus, the future of plant breeding is a challenging task. The deployment of innovative breeding techniques will be a new tool to assist the conventional breeding techniques Undesirable effects Plant breeding has several useful applications in the improvement of crop plants. However, it has five main undesirable effects on crop plants. 1. Reduction in Diversity : Modern improved varieties are more uniform than land races. Thus plant breeding leads to reduction in diversity. The uniform varieties are more prone to the new races of pathogen than land races which have high genetic diversity.
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  4 2. Narrow geneticbase : Uniform varieties have narrow genetic base. Such varieties generally have poor adaptability. 3. Danger of Uniformity : Most of the improved varieties have some common parents in the pedigree which may cause danger of uniformity. 4. Undesirable combinations : Sometimes, plant breeding leads to undesirable combinations. The examples of man made crops having undesirable combination of characters are Raphanobrassica and Pomato. 5. Increased susceptibility to minor diseases and pests : Due to emphasis on breeding for resistance to major diseases and insect pests often resulted in an increased susceptibility to minor diseases and pests. These have gained importance and, in some cases, produced severe epidemics. The epidemic caused by Botrytis cinerea (grey mold) in chickpea during 1980-82 Punjab, Haryana. The severe infection by Karnal bunt (Tilletia sp.) on some wheat varieties, infestation of mealy bugs in Bt cotton.