The platform GrowScreen-Agar enables identification of phenotypic diversity in root and shoot growth traits of agar grown plants

Kerstin A Nagel,Andreas Averesch,Alexander Putz,Frank Gilmer,Hanno Scharr,Ulrich Schurr,Bernd Kastenholz,Achim Walter,Kathrin Heinz,Fabio Fiorani,Andreas Fischbach,Henning Lenz

doi:10.1186/s13007-020-00631-3

Abstract

BackgroundRoot system architecture and especially its plasticity in acclimation to variable environments play a crucial role in the ability of plants to explore and acquire efficiently soil resources and ensure plant productivity. Non-destructive measurement methods are indispensable to quantify dynamic growth traits. For closing the phenotyping gap, we have developed an automated phenotyping platform, GrowScreen-Agar, for non-destructive characterization of root and shoot traits of plants grown in transparent agar medium.ResultsThe phenotyping system is capable to phenotype root systems and correlate them to whole plant development of up to 280 Arabidopsis plants within 15 min. The potential of the platform has been demonstrated by quantifying phenotypic differences within 78 Arabidopsis accessions from the 1001 genomes project. The chosen concept ‘plant-to-sensor’ is based on transporting plants to the imaging position, which allows for flexible experimental size and design. As transporting causes mechanical vibrations of plants, we have validated that daily imaging, and consequently, moving plants has negligible influence on plant development. Plants are cultivated in square Petri dishes modified to allow the shoot to grow in the ambient air while the roots grow inside the Petri dish filled with agar. Because it is common practice in the scientific community to grow Arabidopsis plants completely enclosed in Petri dishes, we compared development of plants that had the shoot inside with that of plants that had the shoot outside the plate. Roots of plants grown completely inside the Petri dish grew 58% slower, produced a 1.8 times higher lateral root density and showed an etiolated shoot whereas plants whose shoot grew outside the plate formed a rosette. In addition, the setup with the shoot growing outside the plate offers the unique option to accurately measure both, leaf and root traits, non-destructively, and treat roots and shoots separately.ConclusionsBecause the GrowScreen-Agar system can be moved from one growth chamber to another, plants can be phenotyped under a wide range of environmental conditions including future climate scenarios. In combination with a measurement throughput enabling phenotyping a large set of mutants or accessions, the platform will contribute to the identification of key genes.

Highlights

Root system architecture and especially its plasticity in acclimation to variable environments play a crucial role in the ability of plants to explore and acquire efficiently soil resources and ensure plant productivity
Stetter et al [45] for example found a large diversity in root hair traits among the investigated 166 accessions which partly overlap with the 78 accession used in our study confirming the large phenotypic variation we found in root growth traits
The phenotyping platform GrowScreen-Agar described in this work is a unique automated prototype to phenotype root and shoot traits of Arabidopsis plants or young seedlings of crop species grown in agar-filled Petri dishes

Summary

Introduction

Root system architecture and especially its plasticity in acclimation to variable environments play a crucial role in the ability of plants to explore and acquire efficiently soil resources and ensure plant productivity. Nagel et al Plant Methods (2020) 16:89 root system architecture to respond dynamically to temporal and spatial changes in soil environments, such as heterogeneously distributed resources [23]. These responses can include growth modifications of different root classes (e.g. primary, seminal, lateral or adventitious roots), branching angles and frequencies of lateral roots or length and density of root hairs. A quantitative description of root and shoot phenotypes of mutants and accessions is fundamental to understand how plants acclimate to a changing environment and to identify genes underlying root system architecture [40]

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Conclusion