Nmg Borralho

Accounting for native stand characteristics in genetic evaluations of open-pollinated progeny from a Eucalyptus globulus base population

A simple classification of the stand characteristics from where open-pollinated seed of Eucalyptus globulus Labill. ssp. globulus has been collected was incorporated in a genetic evaluation model in an attempt to account for the different levels of inbreeding in native stands. Parent trees were grouped into four classes of local stand type, ranging from isolated trees to dense stands. The inclusion of stand type in the model improved significantly the fit and caused a reduction of 4 to 13% in the heritability. Growth was clearly depressed in progeny from isolated trees or remnant stands. Levels of abnormalities in the seedlings varied slightly amongst stand types (p=0.11) but the trend was less obvious. Results suggest that stand type classification accounted for some of the selfing and neighbourhood inbreeding in open-pollinated families. Correlations between breeding values estimated with and without stand type in the model were usually above 0.95 so selection efficiency is likely to be little affected. The approach followed in this paper seems to be a pragmatic way of correcting between potential differences in the levels of inbreeding depression amongst families.