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

Paulo Henrique Ramos Guimarães,Isabela Pereira De Lima,Patrícia Guimarães Santos Melo,Anna Cristina Lanna,Marcel De Raïssac,Adriano Pereira De Castro

doi:10.1186/s12284-020-00404-5

Abstract

BackgroundThe 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.ResultsHigh 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.ConclusionsThis 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.

Highlights

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
The distribution of the root traits was normal overall, with the exception of αFRL20 40, which needed to be transformed by Box-Cox transformation (Box and Cox 1964)
The branching index (BI) was highly variable between accessions and water treatments (CV between 34.7 and 55.4% depending on the layer)

Summary

Introduction

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. The link between root traits and the maintenance of grain yield under drought is complex and needs further investigation before it can be used directly in breeding programs (Dorlodot et al 2007; Kondo et al 2003; Gowda et al 2011; Comas et al 2013; Han et al 2016; Li et al 2017). Under a severe water deficit, the dynamics of root system growth are a key factor for plant adaptation (Matthews et al 1984), as well as its plasticity, which is the ability to modify its growth and structure in varying environments (Price et al 2002a). Changes in plant root system architecture may allow the selection of an ideal root system for different environments, with better nutrient uptake capacity, which would allow higher yield levels even under adverse weather conditions (Lynch 2007)

Methods

Results

Discussion

Conclusion