Famílias Clonais em Eucalyptus

Abstract

Eucalypts (Eucalyptus spp.) is the most cultivated forest genus in Brazil, with 7.5 million acres, and is the main source of products derived from planted forest. Genetic improvement and the cloning technique contributed to the increase in productivity and to the competitiveness of eucalyptus culture in Brazil. However, the low genetic diversity of monoclonal eucalyptus plantations implies risks in the face of new biotic and abiotic challenges. The strategy of clonal families is an alternative to mitigate these risks, due to the greater genetic diversity of the plantations and, consequently, greater safety. In addition to that, clonal families provide increases in productivity and can accelerate the breeding cycle. The objective of this work was to evaluate the feasibility of the clonal family strategy for the improvement and recommendation of genetic materials for Suzano S.A. at Bahia. The clonal

family employed in this study consisted of 249 half-sib clones, selected from the same open- pollinated progeny of E. grandis. In 2014 and 2015, the clonal family was planted in several

operational planting areas, present in different environments of the company in Bahia. For this study, four sites were selected, and in each of them three plots of one hundred plants were established and the diameter at breast height (DBH, cm) of the trees was measured. With the DBH data, the 30 best trees in each plot were selected, and then inventoried for DBH, height (H, m) and mean annual increment (MAI, m3 .ha-1 .year-1 ). The genetic identity of the selected trees was determined using 92 single nucleotide polymorphisms (SNP). The initial clonal families presented competitive productivity compared to the monoclonal operational controls, and the selection of the 30% best trees in the plantation offered significant gains in MAI, while ensuring genetic diversity. SNP genotyping allowed the identification of 42 to 56 clones among the trees selected at each of the four sites. The coincidence between the clones selected at each site was low, and there was no significant correlation between their performances in MAI at the respective locations, indicating the existence of genotype-by-environment interaction between the areas. The selection of the 15 best clones in each location provides the formation of improved clonal families for recommendation on an operational scale, with gains in productivity and genetic diversity. The results corroborate that the strategy of clonal families is promising, as it offers a reduction of time on the genetic improvement pipeline, gains in productivity and greater safety, due to the greater genetic diversity of the plantations.