The hidden half of Brazilian rice: putting roots on the table to better evidence the genetic variability available for breeding

Abstract

Assessing genetic variability is essential to crop breeding and represents the basis for a successful crop selection, including rice (Oryza sativa L.). Root system shows a large range of roles that could be improved genetically. However, it has been virtually neglected by most breeders. The objective was to characterize a selected sample of the Brazilian rice germplasm, regarding on root growth and development, and to combine this data to shoot traits, aiming to depict the genetic variability within this germplasm. Sixteen Brazilian accessions of rice were analyzed with basis on root and shoot traits in two distinct experiments, mainly cultivars launched in the past four decades and presenting unique characteristics. The first experiment was carried out at hydroponic conditions to evaluate the performance of rice accessions during the seedling stage. The second was carried out in long PVC tubes to assay the rice accessions at the reproductive period. Traits were treated individually as well as analyzed jointly by different multivariate methods of genetic variability assessment. Most of the rice accessions showed similar results for a part of the studied traits, however differences were observed for some traits. The clustering methods agreed to group a large number of rice accessions into a single group, distinguishing only the best performing genotypes. Highlighted Conclusions 1) The genetic variability within a group of Brazilian rice accessions is narrow when based on both root and shoot traits. 2) The accessions BRS Pampeira, at seedling period, and BRS Pampa, at reproductive stage, show prominent root performance, being promising parents for breeding programs focused on root system improvements.