FIBER QUALITY INDICES OF Corymbia spp. AND Eucalyptus spp. WOOD FOR THE SELECTION OF GENETIC MATERIALS FOR PULP PRODUCTION

The selection of genetic materials for obtaining cellulosic pulp and paper production necessitates evidence of efficiency in terms of silvicultural performance and industrial processing. In this context, this study aimed to select genetic materials from Eucalyptus spp. and Corymbia spp. for pulp production. The selection was achieved through cluster analysis, based on the morphological traits of the main anatomical elements of the wood, the screened brown pulp yield, and fiber quality indices (Runkel ratio, slenderness ratio, Mulsteph coefficient, and flexibility coefficient). Sixteen genetic materials were evaluated, each represented by three trees of average diameter, collected at 81 months of age with a planting spacing of 6x1.5 m, from plantations located in the municipality of Itamarandiba - MG, Brazil. Axiovision 4.8 software was used to measure the dimensions of fibers and vessels under an optical microscope. Information regarding the screened pulping yield for these genetic materials was obtained from literature. Three distinct groups of genetic materials emerged from cluster analysis. In group I, hybrids with longer and less flexible fibers (Runkel ratio >1, wall fraction >50%, and flexibility coefficient <50%) predominated, making them more suitable for manufacturing absorbent papers. In contrast, groups II and III comprised genetic materials with higher screened yields (>52.0%), lower wall fractions (<50%), and other fiber quality indices indicating a predominance of more flexible fibers (flexibility coefficient >50% and slenderness ratio >51%). These fibers are primarily more suitable for producing tear- and burst-resistant papers, intended for packaging and bags.