Parâmetros genéticos e diversidade genética em matrizes e progênies de meio irmãos de Caryocar brasiliense (pequizeiros) produtores de frutos sem e com espinhos no endocarpo por marcadores fenotípicos e moleculares

Abstract

There are five chapters in this thesis.The pequi tree (Caryocar brasiliense) is a fruit-bearing species native to the Cerrado with several applications. The first chapter conducted a bibliometric review, enabling the identification of gaps in the species' scientific development. These gaps primarily pertain to genetic enhancement and the identification of genetic diversity using molecular markers. We should highlight and encourage further research on these gaps, as they can significantly contribute to conservation and improvement programs for the species. Genetic improvement can contribute to the development of varieties with desirable characteristics, such as greater productivity, resistance to diseases, and better fruit quality. Furthermore, characterization of genetic diversity using molecular markers can facilitate germplasm identification and genotype selection for breeding programs. Continued research in these areas, together with collaboration between scientists, farmers, and policymakers, is essential to promote the conservation, sustainable use, and economic development of pequi as an important natural resource in the Brazilian socioeconomic and environmental context. Chapter 2 explored genetic variability based on traits measured in fruits and pyrenes. We observed clusters and variability among C. brasiliense genotypes, indicating potential genotypes for genetic improvement and conservation programs. We can use clustering patterns to identify groups of individuals with similar genetic traits, which has significant practical implications. The results obtained by different analysis methods, such as Tocher, UPGMA, and principal components, were consistent in identifying genetic diversity among genotypes. By grouping pequi genotypes based on their phenotypic variability, it was possible to select parents that presented desirable traits for fruit production and quality. We can use the high correlation between some traits identified in the study to reduce the number of traits to measure, thereby making the selection process more efficient and focused on the most relevant traits. In Chapter 3, the mixed-model approach using the REML/BLUP method was shown to be a useful way to figure out genetic parameters and variance components in groups of maternal half-sibling pequi trees. This made it possible to predict genetic values and improve the accuracy of selection. The observation of variation among the best progenies over a 24-month period underscores the ongoing significance of estimating genetic parameters in these and future families. In Chapter 4, we evaluated the genetic and phenotypic divergence, as well as the correlations between traits, for selection purposes among families of maternal half-sibs in the juvenile stage. Our multivariate methods generated clusters that allowed us to group the families into distinct groups, thereby demonstrating the genetic diversity present in the studied population. The results obtained can support species genetic improvement programs, allowing genotypes with desirable characteristics to be selected for commercial cultivation. Furthermore, the correlations identified between phenotypic traits contribute to the optimization of selection processes, aiming to develop more productive varieties adapted to cultivation conditions. In Chapter 5, ISSR and SSR molecular markers were used to accurately measure genetic diversity in families with a mother who had half-siblings. This showed how useful these tools are for finding families that are genetically different or similar. This information is essential for genetic improvement and conservation programs of pequi trees, enabling the selection of genotypes with desirable characteristics. The discovery of genetic and phenotypic divergence within families, especially during the juvenile stage, reveals the existence of broad genetic variability.