Unit- 1
Historical development, concept and nature & role of plant breeding, Major achievements and future prospects.
Genetics in relation to plant breeding
Plant breeding may be defined as a technology of developing superior plants for various purposes.
History of plant breeding divided into phases
1. Classical plant breeding (1900 - 1980)
2. Modern plant breeding
A. Classical plant breeding- started after rediscovery of mendel's results in 1900 by three scientist - de Vries - Holland, Correns- Gerany and Tschermark- Austria.
-Uses interbreeding (crossing) of closely or distantly related individual to produce new crop varieties or line with desirable properties.
Major achievements
1 Discoveries/concept developed- like principle of inheritance, progeny selection, individual plant selection, pure line selection, dominance hypothesis etc.
2. Breeding techniques used- Homologous recombination between chromosome to generate genetic diversity. Also used in vitro techniques like protoplast fusion, embryo rescue or mutagenesis.
3. Products developed- Landraces, mass selected varieties and exotic varieties. Later on semi dwarf varieties in wheat and rice, hybrids in maize, pearl millet, sorghum, cotton etc. Pure line varieties
4. Major achievements
I) Development of semi dwarf varieties of wheat and rice resulting in green revolution
Ii) Development of productive hybrids in pearl millet, sorghum, cotton pigeonpea, rice, wheat etc.
B. Modern plant breeding (1980 onwards) - Application of agricultural biotechnology - uses technique of molecular biology to select or in case of genetic modification, to insert, desirable traits into plants.
Major achievement
1. Discoveries/concept developed- transgenic breeding, molecular plant breeding, Terminator technology, Traitor Technology, organic plant breeding and participatory plant breeding.
2. Breeding techniques used- genetic modification, market assisted selection, somatic hybridization, plant tissue culture technique etc.
3. Products developed- transgenic varieties in several crop such as rapeseed and mustard, potato, tobacco, tomato, soybean, sugar beet and hybrids in maize and cotton. Organic varieties in some vegetable crops.
4. Major achievements- Transgenic varieties- resulted in genes evolution.
Objectives of plant breeding
1. Higher yield
2. Quality improvement
3. Resistant to biotic stress
4. Resistance to abiotic stress
5 Wider adaptability
6. Early maturity
7. Insensitivity to temperature and light
8. Synchrocones maturity
9. Desirable agronomic characters
10. Development of toxin free varieties
11. Crop specific objective
12. Multiple cropping system can be adopted.
Practical achievements
1. Improvement in yield- yield of wheat, rice, sorghum and pearl millet doubled.
2. Improvement in quality- elimination of toxic substance Erucic acid from the oil of brassica, has greatly enhance the value of this crop (rape and mustardas a source of edible oil). Neurotoxic level in Kesari dal (Lathyrus saticus) seed have been reduced below the critical level by IAR.
3. Insect and disease resistance value- Resistant value developed. Multiline cultives developed in wheat, Barley and oats and synthetic cultivators in maize.
4. Lodging Resistant varieties- dwarf varieties with stiff straw.
5. Early maturity- 270 - 170 days in cotton, 270 to 120 days in pigeonpea, 307 to 270 in sugar cane, 270 to 180 in castor bean.
It permits multiple crop system reduces cost of pesticide spray.
6. Improvement in adaptability
Future prospects.
1. Ample scope for genetic improvement of pulses and oilseeds crops.
2. In India, considerable area is under rainfed cultivation, need to develop crop cultivars resistant to dropped conditions.
3. Need to develop crop cultivation suitable for climate change caused by global warming.
4. Labour became very expensive. need in many crop to develop varieties suitable for machine harvesting.
5. Develop crop cultivated to tolerate metal toxicity.