Marcadores SNPs para identificação de espécies e híbridos de eucalipto e RNA-seq para identificação de genes associados ao transtorno fisiológico do eucalipto

Abstract

Eucalyptus spp. is an economically important tree genus with about 700 species. Favorable characteristics such as rapid growth, adaptability to different ecosystems, great genetic diversity within and between species, good wood density, and high yield in paper and pulp manufacturing make Eucalyptus important in forestry. Forest product companies and research centers seek new technologies to assist in the genetic improvement of Eucalyptus in the face of new challenges. The application of genomics in Eucalyptus plantation has the main objective of assisting genetic improvement, reducing the time of selection cycles. However, genomics can also be used as a tool in the study of challenges that have not yet been solved. This document points out two challenges of Eucalyptus cultivation and the use of genomic techniques as a tool to help improve the genus. The first article in this thesis brings the identification of species and interspecific hybrids of Eucalyptus based on the use of SNP markers (single nucleotide polymorphism) with wide genome coverage. The second article brings an RNA-seq approach to identify genes and metabolic pathways associated with the physiological disorder of Eucalyptus to illuminate the possible etiological agent of the disease that is still unknown. In the first study, the SNP markers were able to identify most of the species and their interspecific hybrids according to the main phylogenetic classifications of the genus, in addition to comparing the genomic identification with the pedigree annotated by breeders. As the Eucalyptus genus has several species (>600) and complex taxonomic classification, this study offers a molecular alternative for breeders to objectively and accurately identify the genomic composition of their hybrids. Our study shows that the genomic composition of the parents can be different from that expected by the annotations of their pedigree. In the second study, the comparison of gene expression between susceptible and resistant clones showed that the physiological disorder affects several metabolic pathways, therefore, it is a complex disease at the molecular level. Stress signaling pathways, genes related to energy production, and fermentation pathway were differentially expressed between susceptible and resistant clones. Terpenoids and other pathways were also identified as important for the resistance or susceptibility of clones to PDE. Thus, both studies present the use of different genomic techniques and the generation of large databases to help in two important problems for the improvement of Eucalyptus plantations: identification of species and hybrids, and of genes involved in the response of resistant clones to the physiological disorder of Eucalyptus.