Hybridization is one of the ways for breeding new variety by crossing two lines or plants having unlike genetic structure or it is the mating or crossing of two plants or lines of dissimilar genotype in order to combine desirable characters from both gene combinations.
The purpose of hybridization is to create genetic variation. When two plants having unlike genetic structure are crossed, the genes from both the parents are brought together. Segregation and recombination produce many new gene combinations in F2 and the subsequent generation. The degree of variation produced by hybridization in the segregating generation depends upon the number of heterozygous genes in the F1, and this depends upon the number of gene for which two parents differ.
The goal of hybridization may be transfer of one or few qualitative characters, the improvement in one or more quantitative character or the use of F1 as a hybrid variety. These objectives are grouped into two classes.
1) Combination Breeding:
The main purpose of combination breeding is to transfer one or more characters into a single variety, from other varieties. These characteristics may be governed by oligogenes or Polygenes.
2) Transgressive Breeding:
Transgressive breeding aims at improving yield or its contributing character through Transgressive segregation. Transgressive segregation is the production of plants in F2 generation that are superior to both the parents for one or more characters.