Phenotyping Root Systems in a Set of Japonica Rice Accessions: Can Structural Traits Predict the Response to Drought?

Abstract

Background The root system plays a major role in plant growth and development and root system architecture is reported to be the main trait related to plant adaptation to drought. However, phenotyping root systems in situ is not suited to high-throughput methods, leading to the development of non-destructive methods for evaluations in more or less controlled root environments. This study used a root phenotyping platform with a panel of 20 japonica rice accessions in order to: (i) assess their genetic diversity for a set of structural and morphological root traits and classify the different types; (ii) analyze the plastic response of their root system to a water deficit at reproductive phase and (iii) explore the ability of the platform for high-throughput phenotyping of root structure and morphology. Results High variability for the studied root traits was found in the reduced set of accessions. Using eight selected traits under irrigated conditions, five root clusters were found that differed in root thickness, branching index and the pattern of fine and thick root distribution along the profile. When water deficit occurred at reproductive phase, some accessions significantly reduced root growth compared to the irrigated treatment, while others stimulated it. It was found that root cluster, as defined under irrigated conditions, could not predict the plastic response of roots under drought. Conclusions This study revealed the possibility of reconstructing the structure of root systems from scanned images. It was thus possible to significantly class root systems according to simple structural traits, opening up the way for using such a platform for medium to high-throughput phenotyping. The study also highlighted the uncoupling between root structures under non-limiting water conditions and their response to drought.

Root-System Architectures of Two Cuban Rice Cultivars with Salt Stress at Early Development Stages

“…Besides the total network length, the number of fine roots is considered to play a major role in nutrition (especially for P) and water absorption [43]. However, in our study, the root width (ARW) was not affected by salt (Table 3), which can be related to the small diameter of roots with <0.03 mm at this early plant development stage.…”

“…Under field or pot conditions, the complete excavation of a root system is almost impossible with risks of root structure loss. In order to better access the root system, investigations with roots in PVC pipes, hydroponic systems or rhizotrons were carried out [43], and according to Shrestha et al [44], rhizotrons are the preferred method for rice root screening, particularly since root angles can be assessed. According to Ali et al [45] and Rasel et al [46], seedling stage screening is suitable to determine salt-tolerant genotypes because variations in the genotypes on this stage are genetically controlled.…”

Genetic Variability of Arabidopsis thaliana Mature Root System Architecture and Genome-Wide Association Study

“…Had-1b and Wc-1 both had one trait that was not changed under water-limitation compared to the other two accessions. This result is corroborated by the study of Guimarães et al (2020), based on a study of rice japonica accessions, which demonstrated that there was no indication of RSA traits on how plants, even the ones representing the same values of traits, react to water stress.…”

Abiotic Stress and Belowground Microbiome: The Potential of Omics Approaches

“…Greater attention should be focused on enhancing crop adaptation upon diverse environmental stresses by the selection of the best adapted root system on the basis of genetic features or thanks to the "manipulation" of root system traits of crops to grow in nutrient-deficient or drought conditions ( [118] and references therein). Several approaches have been developed for phenotyping root systems [122][123][124][125], although there are very few methods and technologies for high-throughput phenotyping of the root growth in the field, e.g., shovelomics [126] and RootTracker [127]. Recent technological advances in the field of phenomics allow plant breeders to successfully evaluate the root architecture of different crops, at least from younger seedlings in a controlled environment.…”