Mapeamento de associação para caracteres via imagens do sistema radicular de milho tropical sob déficit hídrico em região semiárida

Abstract

Water deficit is one of the factors that most negatively impact agricultural production. Root system characters such as length, surface area, volume, and mass are considered of paramount importance in studies under water restriction conditions, as they play a central role in plant growth, allocation, and acquisition of soil resources. Therefore, the identification of genomic regions and/or genes associated with the expression of the root system under water deficit should allow breeding programs to outline more effective strategies for obtaining tolerant genotypes. In this sense, the objective of the present study was to identify marks and/or genomic regions in tropical maize associated with the root system's responses in contrasting water supply conditions. Seven characters of tropical maize root in the V6 phenological stage (six fully expanded leaves) were evaluated within a public diversity panel composed of 360 lines under ideal water supply (WW) and water deficit (WS) conditions. This panel was evaluated in two experiments over two years (2020 and 2021). The associative mapping (GWAS) was conducted for each character under the conditions of WW and WS by the method of the Circulating Probability Unification of Fixed and Random Model (FarmCPU). Candidate genes were annotated for those characters with significant SNPs using MaizeGDB, based on the reference genome B73 RefGen_v4. 23 SNPs were identified in association with all characters of the root system of tropical maize, 12 of these expressed only in WW, four associated with characters in WW and WS, and seven exclusive to WS. These genes are associated with physiological responses and molecular mechanisms related to water deficit tolerance that can be explored in subsequent studies and breeding programs aimed at obtaining genotypes for this condition.