Hybridization in Plants:
Hybridization is the method of producing new crop varieties by crossing two genetically different parents. As a result of hybridization, the desirable characters of two or more species or varieties are combined together or are transformed from one to the other. Hybridization increases genetic variability.
Uses of Hybridization:
- The main purpose of hybridization is to create variations and to produce varieties suited to particular soils and climates.
- It helps in the improvements of crops and increases in the yield.
- By hybridization, new varieties of wheat, tobacco, mustard etc, have been obtained which are resistant to diseases and drought and give good qualitative and quantitative yields.
- As a result of hybridization between wheat and Rye, a new cereal called triticale has been developed.
Steps in Hybridization:
- Selection of Parents- All the desirable traits which are required in the new crop variety is first listed. The available varieties are searched for those traits. Two or occassionally more types of plants having all the desired traits between them are selected as parents.
- Emasculation- It is the removal of male parts or anthers from the future female parent plants in the young state so as to avoid chances of contamination from their pollen.
- Bagging- Flowers of both male and female parents are kept covered with paper, plastic or polythene bags from the very beginning. This prevents contamination from foreign pollen.
- Crossing or Artificial Pollination- Transfer of pollen grains from a selected male flower to the stigma of the female emasculated flower.
- Harvesting seeds and raising plants- The pollination leads to fertilization and finally seed formation takes place. The seeds are grown into new generation which are called hybrids.
Types of Hybridization:
The plants which are crossed together belong to the same species, different species or different genera. According to this relationship between parental plants, the hybridization may be of the following types-
- Intra-varietal Hybridization– in which the crosses are made between the plants of the same variety. Such crosses are useful only in self-pollinated crops. The controlled crossing within the varieties is only useful to maintain and improve the individual.
- Inter-varietal Hybridization– in which the crosses are made between the plants of two different varieties of the same species and is also known as intra-specific hybridization. In this, desired characters can easily be combined. This makes the basis of improving self-pollinated crops as well as certain cross-pollinated crops. In wheat, tobacco, cotton, tomato etc. inter-varietal crosses have been done to achieve a good yield, resistance to diseases, resistance to drought, good quality, nutritive value etc. Most of the hybrid varieties of cereals have been evolved by this type of hybridization.
- Intergeneric Hybridization– The crosses are made between the plants belonging to two different genera. The disadvantages are hybrid sterility, time-consuming and expensive procedure. Example- Raphanobrassica, Triticale.
- Interspecific Hybridization- The cross between the plants belonging to different species belonging to the same genus is also called intragenic hybridization. It is commonly used for transferring the genes of disease, insect, pest and drought resistance from one species to another. Example– Gossypium hirsutum x Gossypium arboreum.