Aspectos químicos e moleculares do acúmulo de minerais em grãos de arroz

Abstract

The rice crop, considered one of the most economically important cereals, widely cultivated. Despite being a staple food for more than half of the world's population, rice is lacking in essential elements and, on the other hand, can accumulate toxic elements when grown in contaminated areas. Nutritional deficiency may occur due to different minerals, including iron (Fe), which causes serious disorders such as anemia and degenerative diseases. One of the most viable and economical strategies to overcome Fe deficiency is genetic biofortification, which can also be used to reduce the accumulation of toxic elements in rice grains. The characterization of genetic variability makes it possible to identify genotypes that have a higher content of essential elements and a lower concentration of heavy metals, which can be inserted in crossing blocks aiming at the development of biofortified cultivars. Associative mapping is a tool to identify sequences that control traits of interest, helping to overcome obstacles in conventional breeding, and highlighting genes that can be manipulated via transgenics and gene editing. These tools can be used in the development of biofortified cultivars. Thus, the objective of the study was the characterization of rice genotypes regarding the accumulation of minerals and toxic elements in the rice grain; associative mapping for Fe accumulation in rice grains; and the construction of a gene editing plasmid that participates in Fe metabolism. For the first and second studies, a total of 88 accessions of rice were genotyped with 7098 SNPs markers and phenotyped for the concentration of essential elements copper (Cu), iron, manganese (Mn), selenium (Se) and zinc (Zn) and toxic elements arsenic (As), cadmium (Cd) and lead (Pb), in two harvest seasons. It was possible to observe that the genotypes BRS Fronteira, Epagri 108, IRGA 424 CL and Selênio are characterized by presenting less accumulation of As in the grains. The genotypes Epagri 107, Epagri 109 and Irat 162 showed greater accumulation of Zn in the grains. The highest Fe contents were found in the genotypes BRS A701 CL, Carnaroli, Puitá Inta CL and SCS 112. These genotypes can be used in crossing blocks aiming at the development of biofortified cultivars. Thirteen candidate genes associated with Fe accumulation in brown rice grains, which are located on chromosomes 1, 5, 6 and 10, were mapped. In the third study, it was possible to construct a plasmid for editing a gene involved in Fe metabolism. The continuity of this research in the long term may bring more concrete results for the biofortification of Fe in rice.