On estimating components of genetic variance in diallel matings 1

1. The relative importance of additive and non‐additive genetic effects on body weight, egg weight, maturity and rate of egg production were studied from diallel matings in a Leghorn population.

2. From analyses of variance, heritability estimates of the additive fractions, based on half‐sib variances, and the non‐additive or dominance fractions, based on the sire x dam interaction component were obtained.

3. Non‐additive genetic effects were not statistically significant for any of the traits, though for rate of egg production at 32 and 62 weeks, the non‐additive effects as proportion of total variances were 0.29 (P<0.10) and 0.20 (P<0.16), respectively, compared additive effects of 0.08 (NS) and 0.11 (P<0.05).

4. The ratios of non‐additive to additive variances, 1.89 and 3.62 respectively, give support to inbreeding and hybridisation or reciprocal recurrent selection as methods of genetic improvement of egg production.