Variance structure in Eucalyptus hybrid populations

Journal Article

Development

This article presents the analyses of the first mating designs established in the reciprocal recurrent selection scheme of Eucalyptus in Congo. Two selection schemes were involved, the first one concerning E. urophylla • grandis, the second one concerning E. urophylla • pellita . For each of the hybrid species, height, circumference and volume were measured until 3 of 4 years (half of the rotation age). Male additive variance was lower than female additive variance (30% of the additive variance) for the 2 hybrids. It was demonstrated by studying correlation between parent phenotype and parent crossbreeding value in E. urophylla that the higher additive variance for females was probably due to selection of males for their phenotypic value. This result implies a weaker selection intensity for the males in order not to heavily reduce the variability. Variance structure was different according to considered hybrids. For circumference, additive variance accounted for 80% of total genetic variance in E. urophylla • grandis and only 40% in E. urophylla • pellita . Sampling of parents and/or genetic distance between species could be an explanatory factor of this difference.