Ground-Penetrating Radar as phenotyping tool for characterizing intraspecific variability in root traits of a widespread conifer

Abstract

Background and Aim Drought is the main abiotic stress affecting Mediterranean forests. Root systems are responsible for water uptake, but intraspecific variability in tree root morphology is poorly understood mainly owing to sampling difficulties. The aim of this study was to gain knowledge on the adaptive relevance of rooting traits for a widespread pine using a non-invasive, high-throughput phenotyping technique. Methods Ground-Penetrating Radar (GPR) was used to characterize variability in coarse root features (depth, diameter and frequency) among populations of the Mediterranean conifer Pinus halepensis evaluated in a common garden. GPR records were examined in relation to aboveground growth and climate variables at origin of populations. Results Variability was detected for root traits among 56 range-wide populations categorized into 16 ecotypes. Root diameter decreased eastward within the Mediterranean basin. In turn, root frequency, but not depth and diameter, decreased following a northward gradient. Root traits also varied with climatic variables at origin such as the ratio of summer to annual precipitation, summer temperature or solar radiation. Particularly, root frequency increased with aridity, whereas root depth and diameter were maximum for ecotypes occupying the thermal midpoint of the species distribution range. Conclusion GPR is a high-throughput phenotyping tool that allows detection of intraspecific variation in root traits of P. halepensis and its dependencies on eco-geographic characteristics at origin, thereby informing on the adaptive relevance of root systems for the species. It is also potentially suited for inferring population divergence in resource allocation above- and belowground in forest genetic trials.

Understanding role of roots in plant response to drought: Way forward to climate‐resilient crops

“…It is used to analyze the features of RSA and estimate its biomass (Lorenzo et al., 2010). When compared to soil, roots have distinct dielectric permittivity; therefore, GPR is useful for detecting the number, diameter, and depth of coarse roots by measuring the reflected signals produced by hyperbolic reflections on radargrams (Lombardi et al., 2021; Wu et al., 2014). For example, GPR was used to measure coarse roots in plants, including cassava (Delgado et al., 2017) and citrus (Zhan et al., 2019).…”

“…Auxin response factors (ARFs), upon binding to promoters of auxin‐responsive genes, lead to increased tolerance to drought stress in tomatoes (Bouzroud et al., 2018). Auxin promotes the growth of PRs, LRs, and adventitious roots (ARs) (Pierik & Testerink, 2014) and plays an important role in maintaining root architecture in both dicots and monocots (Lombardi et al., 2021). YUCCA (YUC) genes belonging to the family of flavin monoxygenases are key genes involved in auxin biosynthesis (Cheng et al., 2007).…”

Prospects Of Developing Drought Resilience In Crop Plants Through Strategic Modifications In Root System Architecture

“…It is used for analyzing features of RSA and estimation of its biomass (Lorenzo et al 2010). When compared to soil, roots have distinct dielectric permittivity thereby, GPR is useful to detect number, diameter and depth of coarse roots by measuring the reflected signals produced by hyperbolic reflections on radargrams (Wu et al 2014;Lombardi et al, 2021). For example, GPR was used to measure coarse roots in plants, including, cassava (Delgado et al, 2017), citrus (Zhang et al, 2019) and willow (Li et al, 2015).…”

Integrating advancements in root phenotyping and genome‐wide association studies to open the root genetics gateway

“…EIT has been used to observe the development of oilseed rape roots in horticultural compost (Corona-Lopez et al, 2019). In winter wheat and sugar cane, GPR has been used to estimate bulk root biomass and diameter (Liu et al, 2018), as well as intraspecific variation in root traits (Lombardi, Ferrio, et al, 2021). Similarly, hyperspectral imaging is a relatively recent method for phenotyping soil-grown plant roots (Su & Sun, 2019), which can be used to determine more detailed information, such as the water content and root age of a plant.…”