Principles of Plant Breeding (2+1)

Evaluation of inbreds

a) Phenotypic evaluation
Inbreds are evaluated for their phenotypic performance which is most suited for simple inherited traits.

b) Top cross test
Top cross test provides a reliable estimate of GCA. The selected inbreds will be crossed to a tester parent with wide genetic base i.e. open pollinated variety. The hybridprogenies will be evaluated in replicated progeny rows and based on results better inbreds are identified.

c) Single cross evaluation
The developed inbreds can be crossed and the single crosses can be evaluated in replicated trial. Outstanding hybrids tested over years in different locations, are released for cultivation.

d) Prediction of double cross performance
“The predicted performance of any double cross is the average performance of the four non parental single crosses”.

Inbreds: A, B, C, D.

Six possible single crosses = A x B, A x C, A x D, B x C, B x D, C x D.

From these 3 double crosses are produced = (A x B) x (C x D)

(A x C) x (B x D)

(A x D) x (B x C)

The performance of these double cross can be predicted from performance of the four single crosses not involved in producing hybrid.

(A x B) x (C x D)

A x C

A x D

B x C

B x D

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Average

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