A snapshot of the root phenotyping landscape in 2021

Abstract

Root phenotyping describes methods for measuring root properties, or traits. While root phenotyping can be challenging, it is advancing quickly. In order for the field to move forward, it is essential to understand the current state and challenges of root phenotyping, as well as the pressing needs of the root biology community. In this letter, we present and discuss the results of a survey that was created and disseminated by members of the Graduate Student and Postdoc Ambassador Program at the 11th symposium of the International Society of Root Research. This survey aimed to (1) provide an overview of the objectives, biological models and methodological approaches used in root phenotyping studies, and (2) identify the main limitations currently faced by plant scientists with regard to root phenotyping. Our survey highlighted that (1) monocotyledonous crops dominate the root phenotyping landscape, (2) root phenotyping is mainly used to quantify morphological and architectural root traits, (3) 2D root scanning/imaging is the most widely used root phenotyping technique, (4) time-consuming tasks are an important barrier to root phenotyping, (5) there is a need for standardised, high-throughput methods to sample and phenotype roots, particularly under field conditions, and to improve our understanding of trait-function relationships.

Recent advances in methods for in situ root phenotyping

“…The most widely used method for root phenotyping is the 2D root phenotyping platform ( Delory et al, 2022 ). This method consists of a growth system, imaging device, and image processing software.…”

“… Tracy et al (2020) summarized 11 programs that integrated root traits into germplasm for breeding by phenotyping. However, the development of root phenotyping techniques, especially in situ root phenotyping has lagged behind due to hidden nature of the root structure in the soil and the high complexity of the root system ( Lynch, 2021 ; Delory et al, 2022 ). There is an urgent need to establish accurate and efficient root phenotyping technologies for measuring root properties, including root system architecture and morphology under various stresses ( McCormack et al, 2017 ).…”

Root biology never sleeps

“…S2. The availability of standardised protocols for root collection and trait measurement was also highlighted by the participants of the online survey, organised by the Ambassadors in addition to the Symposium (Delory et al ., 2022) and the workshop as an important issue for future research. The Root Ecology Handbook recently published in New Phytologist provides a comprehensive guide on root sampling, processing and measuring for a wide variety of traits in a standardised manner (Freschet et al ., 2021).…”

“…Further phenotyping approaches such as the measurement of ion uptake rates and mechanical measurements were also discussed throughout the meeting. A detailed list can be found in the results of the phenotyping survey (Delory et al ., 2022). [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…Detailed image‐based root phenotyping techniques such as X‐ray computed tomography (CT) scanning can improve our interpretation of in‐field studies (C. Topp, Donald Danforth Plant Science Center, MO, USA). Current advances allow high‐resolution and/or high‐throughput phenotyping studies, even in mature crops and under field conditions (Gore et al ., 2020; Rich et al ., 2020), although methodological challenges remain (Delory et al ., 2022). For example, root phenotyping of rooting depth and its significance for deep water or nitrate uptake is being addressed with large‐scale field experiments using minirhizotrons or soil coring on maize (A. Leakey, University of Illinois, USA), wheat (J. Christopher, University of Queensland, Australia) and potatoes (O. Popovic, Copenhagen University, Denmark).…”