Fenotipagem, genotipagem e mapeamento de características de importância agronômica em arroz

Abstract

In rice, productivity is a complex characteristic, influenced by different components. Identifying genes that control these characteristics is important for obtaining more productive cultivars. In its cultivation environment, rice can have its productivity reduced by biotic and abiotic stresses, such as salinity. With the advancement of biotechnology tools, such as genotyping using high-density SNPs (single nucleotide polymorphism) markers, rice genomic studies were boosted, helping breeders. In recent decades, genome-wide association studies have been frequently used in rice to identify SNPs. However, there are few reports on the use of Brazilian rice germplasm in these studies. Therefore, the objective of this work was the genotyping, phenotyping and mapping of characteristics of agronomic interest in rice germplasm used in Brazil. For this, a collection of 188 rice accessions cultivated in the country was used. This collection was genotyped with 7098 SNP markers. Genotyping was used to estimate genetic variability, in addition to population structure and genotype relatedness, which were used in the mapping study. Rice accessions were phenotyped for salinity tolerance at the reproductive stage, evaluating the number of panicles per plant, number of sterile panicles per plant and percentage of sterility of the main panicle. For the mapping study, the accessions were phenotyped for plant height, number of tillers, number of panicles per plant, main panicle length, main panicle weight, number of full grains in the main panicle, number of sterile grains in the main panicle, grain weight of the main panicle, weight of one hundred grains and productivity per plant. Based on genotyping, it was observed that the accessions used present little genetic variability, as the population structure, principal component analysis (PCA) and phylogenetic tree were divided into two groups. Considering the phenotyping study for salinity tolerance at the reproductive stage, it was found that the majority of genotypes were severely affected by stress, with a high number of completely sterile panicles. For the associative mapping study using PCA, 65 significant SNP markers were identified and using the population structure, 175 significant SNP markers were identified, totaling 622 genes annotated close to these significant SNPs.