Principles of Genetics and Breeding

11.1.8 Specific combining ability

• When the lines are crossed among themselves, the superiority or inferiority of a cross over the mean of all crosses indicates the specific combining ability (SCA) of the cross.
• This is due to the non-additive genetic effect in a character.
• When the lines or sub-populations are mated in all possible combinations, it is known as ‘diallel mating’.
• In a diallel mating design it is possible to calculate the GCA of the lines and SCA of the crosses.
• It is done to test the performance of the lines in cross combinations.
• For example the cross breeding programme of rohu originated from different rivers carried out at CIFA is a method of diallel crossing.