An index combining volume and Pilodyn penetration to study stability and adaptability of Eucalyptus multi-species hybrids in Rio Grande do Sul, Brazil

Abstract

ABSTRACTThis paper presents results from a study into the stability and adaptability of Eucalyptus multi-species hybrids in the state of Rio Grande do Sul, Brazil, using an index that includes volume growth and Pilodyn penetration. Clonal tests were established with 146 Eucalyptus clones from 34 different species and/or hybrids, in a randomised block design with 30 replications, and one plant per plot in four different sites. Diameter at breast height (dbh), tree total height (th), and Pilodyn penetration for indirect estimate of basic density were measured in trees at three years of age. An index (MAIweight) combining mean annual volume increment and Pilodyn penetration was calculated. In the analysis of MAIweight for each site, the best clones were from pure species (E. urophylla, E. grandis and E. saligna). In contrast, the evaluation of adaptability and stability between the four environments simultaneously showed that three-way cross and single cross hybrids ranked more highly: E. urophylla × (E. camaldulensis × E. grandis), E. grandis × (E. urophylla × E. grandis) and E. grandis × E. urophylla. This study demonstrates the importance of heterosis (hybrid vigour) to improving adaptability and stability. Genetic complementarity from crosses between different species was the principal process that produced the observed heterosis. While the pure species performed well in specific environments, the hybrids presented better broad adaptation to a range of environments. Breeding efforts should therefore account for these features when planning crosses and choosing sites for establishing trials.