Caracterização fenotípica e molecular da diversidade genética em linhagens elite de arroz de terras altas

Abstract

Rice (Oryza sativa L.) is one of the most cultivated and consumed cereals worldwide. In Brazil, to face the challenge of maintaining rice grain production, genetic breeding stands out as one of the most effective strategies. Genetic variability corresponds to the raw material for breeders to carry out selections in breeding programs. In addition, knowledge of this variability allows for the positioning of contrasting and complementary lines with greater precision for crossbreeding blocks. Thus, the objective is to study the genetic diversity existing among the elite lines of the Upland Rice Genetic Breeding Program of the Federal University of Lavras. In total, in the Cultivation and Use Value (VCU) trials including the 2023/24 and 2024/25 harvests, 27 lines were evaluated, whose characterization involved phenotypic and molecular analyses. For phenotypic analyses, the experiments were conducted in two locations during the 2023/2024 season: Lambari/MG and Patos de Minas/MG. In the 2024/25, the experiment was conducted only in the city of Lavras/MG. A randomized block design (DBC) with three replications was used, and the plots consisted of five 4 m rows, with 0.25 m spacing and a sowing density of 90 seeds/m. During the trials, the following characteristics were evaluated: number of days to flowering (DEF), grain yield (kg.ha-1 ), plant height (cm), milling rice yield and head rice yield (%). The data generated were subjected to joint analysis and analyzed using the mixed models approach. The BLUP averages were estimated to predict the performance of the genotypes using the R software. The 27 lines were grown in trays in the greenhouse of UFLA until the ideal stage for leaf collection. DNA extraction took place at the Molecular Genetics Laboratory of UFLA, and samples were sent to Embrapa Rice and Bean for amplification via PCR in three multiplex SSR panels, with eight markers each. Genotyping was performed by capillary electrophoresis (3500xL sequencer) and the fragments were analyzed in GeneMapper. The data were processed using the R software. Of the 24 microsatellite markers (SSR) initially used, 22 showed satisfactory amplification, a total of 81 alleles were detected, with a variation of 1 to 7 alleles per locus, resulting in an average of 3.68 alleles per marker. The observed heterozygosity (0.13) was lower than expected (0.45), and the inbreeding coefficient was high (0.72), indicating the presence of a large number of homozygous loci. The results obtained in this study demonstrate the existence of broad genetic diversity and phenotypic variability among the elite upland rice lines evaluated. It was possible to identify genotypes with superior performance for the characteristics of interest in rice cultivation, evidencing their potential use as future commercial cultivars or strategic parents in breeding programs, due to the assured genetic diversity, due to the use of phenotypic data in selection by independent levels of elimination, associated with molecular grouping, ensuring the choice of lines with good performance and distinct genetic groups. Among the highlights are the lines BRS-Esmeralda, BRSMG Caçula, CNAx20665-B-10, CNAx20665-B-1, CNAx20658-B-12, CNAx20650-B-17, CNAx20665-B-5, CNAx20651-B-29, CNAx20665-B-15, CNAx20651-B- 7, MP2021-129-3, MP1920-39-4, MP1920-43-3, MP1819-106-8, MP1920-86-5.