Diallel cross explained

A diallel cross is a mating scheme used by plant and animal breeders, as well as geneticists, to investigate the genetic underpinnings of quantitative traits.^{[1] [2]}

In a full diallel, all parents are crossed to make hybrids in all possible combinations. Variations include half diallels with and without parents, omitting reciprocal crosses.^[3] Full diallels require twice as many crosses and entries in experiments, but allow for testing for maternal and paternal effects.^[4] If such "reciprocal" effects are assumed to be negligible, then a half diallel without reciprocals can be effective.

Common analysis methods utilize general linear models to identify heterotic groups,^[5] estimate general or specific combining ability,^{[6] [7]} interactions with testing environments and years, or estimates of additive, dominant, and epistatic genetic effects^{[8] [9]} and genetic correlations.^[10]

Mating designs

There are four main types of diallel mating design:

1. Full diallel with parents and reciprocal F1 crosses
2. Full diallel as above, but excluding parents
3. Half diallel with parents, but without reciprocal crosses
4. Half diallel without parents or reciprocal crosses

Notes and References

1. Hallauer, A. R. and J. B. Miranda Filho. 1988 Quantitative genetics in maize breeding. 2nd ed. Iowa State University Press, Ames, IO.
2. . The replicated diallel cross: a generalized method of analysis . . 14 . 1 . 81–104 . January 1984 . 6712552 . 10.1007/BF01066070. 26899703 .
3. 10.1038/hdy.1965.12 . Analysis of variance of the half diallel table . 1965 . Jones . R. M. . Heredity . 20 . 117–121 . 1. free .
4. Crusio WE . A note on the analysis of reciprocal effects in diallel crosses . . 66 . 3 . 177–185 . December 1987 . 10.1007/BF02927711. 35147905 . 2009-08-14.
5. Griffing, B. 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Australian Journal of Biological Sciences 9: 463-493
6. Gardner, C. O. and S. A. Eberhart. 1966. Analysis and interpretation of the variety cross diallel and related populations. Biometrics 22: 439-452
7. Sprague G. F., and L. A. Tatum. 1942. General vs. specific combining ability in single crosses of corn. J. Am. Soc. Agron. 34: 923-932
8. Hayman, B. I. 1954. The analysis of variance of diallel tables. Biometrics 10: 235-244
9. Hayman BI . The theory and analysis of diallel crosses . . 39 . 6 . 789–809 . November 1954 . 10.1093/genetics/39.6.789 . 17247520 . 1209689 . 2010-03-02.
10. Crusio WE . Bi- and multivariate analyses of diallel crosses: a tool for the genetic dissection of neurobehavioral phenotypes . . 23 . 1 . 59–67 . January 1993 . 8476392 . 10.1007/BF01067554. 37158435 .