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

Abstract

Soybean [Glycine max (L.) Merr] is the legume with the largest cultivated area worldwide and its yield depends largely on symbiotic nitrogen fixation and root architecture. This study aimed to explore the genetic variability of root architectural traits and di-nitrogen fixing activity in a small collection of nine European cultivars belonging to the same maturity group during their early stages. New image analysis approaches were implemented to characterise root architecture at high throughput. Significant genetic variability was identified for the width of the root system, root density, and for nitrogen fixation. This study allowed us to highlight trade-offs among root and nodule traits, and structural and functional traits. Finally, both the image analysis approach and the results could be used for breeding programs of soybean, that could take into account the root system architecture, when the plant interacts in symbiosis with N2-fixing bacteria.

Genotypic differences in root traits to design drought-avoiding soybean ideotypes

“…A number of previous studies reported a variability in root traits among soybean cultivars. This variability was observed during early growth (Allmaras et al, 1975;Kaspar et al, 1978Kaspar et al, , 1984Zhao, 2004;Ao et al, 2010;Manavalan et al, 2010;Matsuo et al, 2013;Fenta et al, 2014;Thu et al, 2014;Fried et al, 2018Fried et al, , 2019Mwamlima et al, 2019;Falk et al, 2020;Gao et al, 2020;Dayoub et al, 2021;Maslard et al, 2021), at flowering stage (Zhao et al, 2004;Mwamlima et al, 2019) or at maturity (Ao et al, 2010). Phenotypic differences among soybean cultivars for root traits have been well documented under different conditions (drought, phosphorus availability) across many locations worldwide (Tabs.…”

“…A wide genetic variability has been reported for most investigated architectural and morphological root traits during early growth (~stage V3) regardless of water regime or soil status. Architectural root traits such as rooting depth, root angle and root width were significantly different among cultivars, irrespective of the water regime and growth environment (Matsuo et al, 2013;Fenta et al, 2014;Falk et al, 2020;Maslard et al, 2021). Root morphological traits as root surface, root volume, taproot length, root tips number and total root length were also different among cultivars (Fenta et al, 2014;Fried et al, 2018Fried et al, , 2019Falk et al, 2020;Dayoub et al, 2021).…”

“…Although these techniques may not accurately reflect rooting system morphology and architecture under field conditions, they can be proposed as complementary approaches to overcome field limitations. Under greenhouse environment, new image analysis approaches were also implemented to characterize soybean root architectural traits at high throughput (Maslard et al, 2021). Although root phenotyping under controlled conditions is a rapid, low-cost and adaptable method, further experiments are required under field conditions to evaluate the performance of cultivars and to show how shoot and root traits are affected by various soil, climate and management conditions.…”

“…2 and 3). In contrast, only a few studies focused on soybean cultivars commonly grown in Europe (Dayoub et al, 2021;Maslard et al, 2021). For most investigated root traits in the literature (Tabs.…”

“…Little is known to date on how symbiosis modifies root growth and architecture in soybean (Concha and Doerner, 2020;Maslard et al, 2021). Moreover, the correlations between the frequency and intensity of nodulation and root growth are still poorly understood, particularly the factors that control nodule density per unit root length in the absence or presence of stress (Kunert et al, 2016).…”