Principles of Plant Breeding (2+1)

Recurrent selection for specific combining ability

• It was proposed by Hull in 1945 with an objective is to isolate lines from a population that will combine very well with a given inbred. Large part of the heterosis is due to non additive gene action i.e. Dominance and epistasis. So it depends on specific gene combination and is designed as specific combining ability. The inbred is used as tester to isolated lines with high specific combining ability.

First Year:
Several plants are selected from the population and self pollinated. Selected plants used as males are also crossed to an outstanding inbred used as the tester.

Second Year:
Replicated yield trial is planted using test cross progeny.

Third Year:
Selfed seeds from the outstanding progenies are planted in separate progeny rows in a crossing block. All possible inter cross are made by hand. Equal amount of seed from the inter crosses are composited. This completes the original selection cycle.

Fourth Year:
The composited inter cross is planted and the operation of the first year are repeated.

Fifth Year:
Evaluation under replicated yield trial.

Sixth Year:
Selfed seed from outstanding progenies are planted and crossed in all possible intercrosses are composited. The cycle may be repeated.