What is plant breeding?
Plant breeding is the purposeful technique of using plant species in order to produce genotypes and phenotypes of desired characters and traits for specific purposes.
This manipulation involves either genetic engineering, controlled pollination, or both. This is followed by the artificial selection of progeny. Plant breeding often leads to plant domestication.
Choice of Plant Breeding
Plant breeders choose plant breeding for the following reasons:
- To increase the quality and yield of the crop
- Plants have increased tolerance against environmental pressures such as severe temperature conditions, extreme droughts, salinity, etc.
- Plants will have resistance against disease-causing agents such as viruses, bacteria, and fungi
- Increased resistance and tolerance to insect pests
- Increased tolerance of herbicides
Method of Plant Breeding
The basis of all plant breeding is selection or choosing out plants. These selected plants contain desired traits with the best combination of agricultural and quality characters. Seeds from these plants are used in the production of the next generation.
There are three categories of conventional plant breeding:
- First category is self-pollinated plant species. Fertilization follows the germination of pollen on stigmas of the same plant on which it was produced.
- Then comes the second category of species sets seeds by cross-pollination. The fertilization follows the germination of pollen on stigmas of different plants.
- The third and final category is of the species that are asexually propagated. The commercial crop results from planting vegetative parts or by grafting.
Types of Crosses in Plant Breeding
Following types of crosses are used in bred plants.
The type of breeding used for self-pollinating plant species is back-crossing. This type is used when the existing variety is predominantly satisfactory. But it lacks some useful and inherited traits. This trait is found in some other variety.
Hybrids are made between these two varieties. The first hybrid generation is crossed or backcrossed with satisfactory variety which is called the recurrent parent. Backcrossing is very useful and has been extensively used in adding resistance to diseases like rust, smut, mildew, etc.
Pedigree breeding is achieved by artificially hybridizing between parental varieties having different desirable quality traits and characters. This is the most commonly used method in plant breeding.
The self-pollinating plant species such as barley, oats, wheat, and many edible legumes have great significance. Once they are genetically pure, varieties can be maintained without change for many generations.
Natural populations of cross-pollinating plant species possess great genetic diversity. No seed parent is true-breeding. In such plants, a system is formed in which hybrid vigor is exploited.
Varieties of asexually propagated plants consist of a large number of genetically identical plants. There are only two ways of introducing new and improved varieties. One is by sexual reproduction and the other is by the isolation of somatic mutations.
The latter method is frequently used successfully for the production of ornamental plants such as chrysanthemum. New forms of potato have occasionally arisen in this way. When sexual reproduction is used, hybrids of existing varieties are reproduced on large scale.
Cell technologies are also been used to extend the range and efficiency of asexual plant propagation.