Early-Stage Phenotyping of Root Traits Provides Insights into the Drought Tolerance Level of Soybean Cultivars

Abstract

Soybean (Glycine max (L.) Merr.) may contribute to the agro-ecological transition of cropping systems in Europe, but its productivity is severely affected by summer drought. New drought-avoidance cropping strategies, such as early sowing, require cultivars with high early plant growth under suboptimal conditions. This study aims at phenotyping early-stage root and shoot traits of 10 cultivars commonly grown in Europe. Cultivars were grown in minirhizotrons under two soil moisture status in controlled conditions. Root and shoot traits were evaluated at 10 days after sowing. Field early growth of two cultivars was also analyzed under early and conventional sowing dates. A significant intraspecific variability (p < 0.05) was found for most investigated shoot and root morpho-physiological traits regardless of the soil moisture status under controlled conditions. However, no significant difference among cultivars (p > 0.05) was found in terms of root architectural traits that were mainly affected by water stress. Total root length was positively correlated with shoot length and shoot dry matter (p < 0.05). Under field conditions, the differences between cultivars were expressed by the canopy cover at emergence, which determines the subsequent canopy cover dynamics. The significant early growth difference among cultivars was not related to the maturity group. Cultivars characterized by high root depth and length, high root density and narrow root angle could be considered as good candidates to cope with water stress via better soil exploration. New agronomic strategies mobilizing the diversity of cultivars could thus be tested to improve soybean water use efficiency in response to climate change.

Genome-Wide Association Study of Root and Shoot Related Traits in Spring Soybean (Glycine max L.) at Seedling Stages Using SLAF-Seq

“…Several studies in crops have emphasized that a deeper root system is influenced by root dry weight and total root length, important for improving drought tolerance and being associated with the final yield under drought stress in soybean ( Hudak and Patterson, 1995 ) and rice ( Bengough et al, 2011 ; Suji et al, 2012 ). Therefore, identifying ideotypes for root traits involved in drought tolerance at early growth stages could be very useful in guiding the development of soybean cultivars with enhanced soil exploration, and thus water acquisition, under water deficit conditions ( Dayoub et al, 2021 ). In this study, four soybean genotypes including Z166, Z201, Z203 and Z232 with promising root structure were identified.…”

“…Due to the challenge in achieving reliable root trait data from the field, characterizing crops like soybean with improved root system characteristics in the field remains still a major defy to current plant biology and, root phenotyping studies are commonly conducted under controlled environments ( Rong et al, 2011 ; Seck et al, 2020 ; Chen et al, 2021 ). Besides, some pieces of evidence support that high yielding soybean varieties are supposed to have propitious root systems at the early stages, which may strongly sustain water and nutrients, resulting in increased yield especially under limited water or nutrient availability ( Seck et al, 2020 ; Chen et al, 2021 ; Dayoub et al, 2021 ). To date, several Quantitative Trait Loci (QTL) studies have been conducted to locate shoot and root-related trait QTLs in soybean under various conditions of growth, at diverse developmental stages and involving various genetic populations ( Rong et al, 2011 ; Brensha et al, 2012 ; Manavalan et al, 2015 ; Prince et al, 2020 ; Seck et al, 2020 ; Chen et al, 2021 ).…”

Towards Developing Drought-smart Soybeans

“…Early maturing varieties belong to groups 0 to 3, whereas late-maturing varieties fall in groups 6 and onwards (Zhang et al, 2007;Yang et al, 2019). Drought impacts soybeans cultivars differently, as some cultivars are more susceptible than others (Oya et al, 2004;Maleki et al, 2013;Du et al, 2020;Dayoub et al, 2021). Also, the timing of drought stress, whether at the vegetative or the reproductive phase, is important in determining yield loss.…”

Root architecture characterization in relation to biomass allocation and biological nitrogen fixation in a collection of European soybean genotypes

“…In order to quantify the genetic variability of root and nodule traits, we decided (i) to analyse structural (including biomass allocation, morphological characterization) and functional (N 2 fixation) traits and (ii) to focus on a small collection of nine varieties belonging to the same maturity group. This choice was motivated by the need to compare root traits from plants at the same developmental stage, and was supported by a first study conducted by Dayoub et al (2021). The full dataset is provided in Supplemental Material Table S1.…”

“…The genetic variability of root architecture in soybeans has been evaluated in different maturity groups, and has highlighted a significant variability of root traits during their early growth (Falk et al, 2020;Dayoub et al, 2021). Some of these variables have also been correlated with aerial traits, such as the root length which was positively correlated with shoot dry matter (Dayoub et al, 2021). These studies provided very interesting results by revealing the root growth potential of each of the genotypes.…”