Types of Hybridization
Based on the taxonomic relationship of the two parents, hybridization may be classified into two broad groups.
1) Intervarietal Hybridization:
The parents involved in hybridization belong to the same species. In crop improvement programme this type of hybridization is commonly used E. g crossing of two varieties of wheat or other crops. The Intervarietal crosses may be simple or complex depending upon the number of parents involved.
a) Simple Cross:
In simple cross, two parents are crossed to produce the F1. The F1 is self to produce F2 or is used in a back cross programme.
E .g A X B
F1 (AX B)
b) Complex Cross:
More than two parents are crossed to produce the F1 hybrid, which is then used to produce F2 or used in back cross. The cross is also known as convergent cross, because it brings genes from several parents into a single hybrid.
E.g A, B, C (Three Parents)
A X B
F1: (A X B) X C = Complex hybrid (AX B) X C
Ex: Four Parents (A, B, C, D)
A X B C X D
Complex hybrid (A X B) X (C X D)
Ex. Eight parent (A, B, C, D, E, F, G, H)
A X B C X D E X F G X H
F1: (A X B) X (C X D) X (E X F) X (G X H)
Complex hybrid < (AX B) X (C X D)> X <( E X F) X ( G X H)>
2) Distant Hybridization:
The parents involved belong to the different species of the same genus or of different genera. When two different species of the same genes are crossed known as inter specific hybridization. Ex. Sugarcane varieties have been developed by crossing Saccharum oficinarum X Saccharum barberi, while in cotton G.arboreum X G. hirsutum. When two different species belongs to different genera known as Intergeneric hybridization. Ex. Triticale is developed by crossing Triticum aestivum X secale cereal (Rye). Generally the objectives of such crosses are to transfer one or few characters, like disease resistance.