Heterozygosity and biomass production in Salix eriocephala

The relationships between heterozygosity at 11 variable isoenzyme loci and total above-ground leafless biomass production were examined in four full-sib families of Salix eriocephala, a willow species important in short-rotation intensive-culture feedstock plantations. Relationships were investigated by comparing the performance of heterozygotes with that of corresponding homozygotes in locus-by-locus comparisons, by investigating multiple regression models with individual loci as independent variables, and by employing the adaptive distance model. In all of these analytical approaches, evidence indicated the presence of positive associations between heterozygosity at enzyme loci and biomass production. The theoretical implications of these results are discussed in the specific context of this study.