Genetic evaluation and selection of eucalyptus for pulp production

Brazil holds the largest planted forest area in the world, and Eucalyptus plantations are the backbone of the national pulp and paper industry, a position sustained by continuous genetic breeding. The growing global demand for short-fiber pulp requires increasingly productive and uniform plantations, which depends on the development of genetic materials combining fast growth, high wood quality and adaptation to local edaphoclimatic conditions. In this context, progeny tests are fundamental to estimate genetic parameters, quantify available genetic variability and support efficient selection strategies. The objective of this study was to genetically evaluate full-sib eucalyptus progenies in a progeny test and to select superior families and individual trees for cellulose production, supporting clonal and seminal breeding programs. Specifically, the study aimed to estimate genetic and environmental parameters of cellulose production, quantify genetic variability among and within families, and identify the best genetic materials for cloning and improved seed production. A progeny test was conducted in the municipality of Araçás, Bahia, Brazil, using a randomized complete block design with five blocks, 182 full-sib families derived from controlled crosses with known parents, and eight plants per plot. The region has a tropical humid climate, with a mean annual temperature of 24.6 °C and mean annual precipitation ranging from 1,050 to 1,340 mm. At three years of age, in January 2024, dendrometric traits (tree height and diameter at breast height) and wood technological traits (basic wood density and air-dry cellulose yield) were evaluated, from which cellulose production per tree was estimated in tons of air-dry cellulose per hectare per year (TSA). Analysis of variance for TSA indicated a highly significant effect of genotypes, with substantial variation both among and within families, demonstrating the existence of relevant genetic variability for selection. The overall mean was 4.48 TSA, with an experimental coefficient of variation of 25.42%, indicating moderate experimental precision. Estimates of genetic parameters showed a heritability of 0.3926 for family means and lower values for selection within families (0.1797) and for individuals in the block (0.231) and in the experiment (0.2297), confirming greater efficiency of selection among families. Genetic coefficients of variation among and within families were 30.55% and 44.34%, respectively, indicating ample genetic variability for continued selection. Using the combined selection procedure in the Genes software from the Federal University of Viçosa, the ten best families were identified as 44, 131, 14, 15, 179, 127, 8, 43, 81, and 114. The five best individual trees, with TSA values ranging from 14.80 to 16.13, were identified as candidates for cloning and for initiating a clonal program to produce improved planting stock and establish clonal plantations. These results indicate that selection of superior families can support improved seed production programs, allowing the company to repeatedly produce seeds from specific crosses to which it has exclusive access to the parental genotypes. At the same time, individual selection of promising trees can enable the establishment of clonal plantations with higher productive potential for the cellulose industry, significantly increasing cellulose yield per hectare.