Diallel Cross Analysis

Free diallel analysis online with Griffing methods 1 to 4, GCA, SCA, reciprocal effects and SE.

Open the Diallel Analysis (Griffing all 4 methods) calculator

When to use it

Use for diallel mating designs in plant or animal breeding. All four Griffing (1956) methods are supported: Method 1 (parents + F1 + reciprocals), Method 2 (parents + F1 only), Method 3 (F1 + reciprocals only), Method 4 (F1 only). Use to decompose treatment variation into general combining ability (GCA), specific combining ability (SCA), and reciprocal effects.

When NOT to use it

Do not use when only some crosses were made; use a partial diallel (Kempthorne and Curnow) instead. Do not use when crosses were not made systematically across all parent pairs. Method 1 needs every cell in the n by n cross matrix; Method 4 needs only the upper triangle.

What you get

ANOVA partition into GCA, SCA, reciprocal (where applicable), and error. GCA estimate per parent with SE and t-test against zero. SCA estimate per cross with SE and t-test. Estimates of sigma-squared GCA and sigma-squared SCA, the GCA-to-SCA variance ratio, narrow-sense heritability under model assumptions.

How to interpret the output

A parent with positive significant GCA for grain yield is a good general combiner; cross it broadly. A cross with positive significant SCA is a specific combination worth advancing as a hybrid. The GCA-to-SCA variance ratio indicates the type of gene action: a large ratio favours additive selection (recurrent selection of parents), a small ratio favours specific cross combinations (hybrid breeding). Sprague and Tatum (1942) introduced the GCA / SCA partition; Griffing (1956) gave the four estimation methods.

Common pitfalls

Picking a method that does not match what was actually planted.
Reporting GCA and SCA without their SEs.
Treating a single trial's heritability estimate as if it generalised to other environments.
Confusing GCA with parent per se performance (GCA is the cross average, not the inbred per se).

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Open Diallel Analysis (Griffing all 4 methods)

References

Griffing, B. (1956). Concept of general and specific combining ability in relation to diallel crossing systems. Australian Journal of Biological Sciences, 9(4), 463 to 493.
Sprague, G. F. and Tatum, L. A. (1942). General vs specific combining ability in single crosses of corn. Agronomy Journal, 34(10), 923 to 932.
Singh, R. K. and Chaudhary, B. D. (1979). Biometrical Methods in Quantitative Genetic Analysis. Kalyani Publishers, New Delhi.