Root Phenotyping for Drought Tolerance: A Review

Allah Wasaya,Xiying Zhang,Zongzheng Yan,Qin Fang

doi:10.3390/agronomy8110241

Abstract

Plant roots play a significant role in plant growth by exploiting soil resources via the uptake of water and nutrients. Root traits such as fine root diameter, specific root length, specific root area, root angle, and root length density are considered useful traits for improving plant productivity under drought conditions. Therefore, understanding interactions between roots and their surrounding soil environment is important, which can be improved through root phenotyping. With the advancement in technologies, many tools have been developed for root phenotyping. Canopy temperature depression (CTD) has been considered a good technique for field phenotyping of crops under drought and is used to estimate crop yield as well as root traits in relation to drought tolerance. Both laboratory and field-based methods for phenotyping root traits have been developed including soil sampling, mini-rhizotron, rhizotrons, thermography and non-soil techniques. Recently, a non-invasive approach of X-ray computed tomography (CT) has provided a break-through to study the root architecture in three dimensions (3-D). This review summarizes methods for root phenotyping. On the basis of this review, it can be concluded that root traits are useful characters to be included in future breeding programs and for selecting better cultivars to increase crop yield under water-limited environments.

Highlights

Drought is a major yield-limiting factor throughout the world [1,2], and is a widespread limitation for cereals production especially under dry land conditions [3,4,5,6]
This review mainly focuses on root traits which are useful for improving crop productivity under drought situation and their phenotyping through non-invasive techniques to save time
It is observed from previous studies that different root traits such as fine root diameter, specific root length and area, root angle, and root length density are useful for improving plant’s productivity under drought conditions

Summary

Introduction

Drought is a major yield-limiting factor throughout the world [1,2], and is a widespread limitation for cereals production especially under dry land conditions [3,4,5,6]. The root system architecture (RSA) is affected by various factors such as soil temperature, moisture, nutrients and soil pH [18,19] which greatly affects crop growth and yield [20,21] Several root characters such as morphological plasticity [22,23], root tip diameter [24], gravitropism [25], and rhizosheaths [26]. As single root morphology has scarcely been considered for plant’s adaptation strategy to drought conditions, different types of roots can be characterized by various traits [35] to determine the ability of various root classes for water uptake [36]. It is observed from previous studies that different root traits such as fine root diameter, specific root length and area, root angle, and root length density are useful for improving plant’s productivity under drought conditions. It is suggested that all these root traits may be included in breeding programs to improve crop productivity under drought conditions

Root Traits Related to Water and Nutrient Uptake and Drought Tolerance

Techniques Used for Root Phenotyping under Controlled and Field Conditions

Limitations

Findings

Conclusions