Identification of Plant Compounds Involved in the Microbe-Plant Communication During the Coinoculation of Soybean with Bradyrhizobium elkanii and Delftia sp. strain JD2

Abstract

Delftia sp. strain JD2 is a betaproteobacterium characterized as a plant growth-promoting bacterium with a 'helper' function, enhancing the performance of rhizobial inoculant strains during the coinoculation of alfalfa and clover. In this work we analyzed i) the effect of the coinoculation with Bradyrhizobium elkanii and Delftia sp. strain JD2 strains on the performance of soybean plants and ii) the production of a few secondary plant metabolites that would explain the positive effect of coinoculation on the growth and development of soybean plants. The results showed a beneficial effect of coinoculation on soybean growth, nodulation rate, and pulse yield, with the concomitant benefit for the agricultural economy. In addition, based on a metabolomics approach, we demonstrated that a different pattern of plant metabolites is being produced at different stages of plant growth. The new information suggests that the coinoculation of soybean changes the primary and secondary metabolism of the plant, including changes in the metabolic status of main and secondary nodules within the plant. The relevance of producing a different pattern of photosynthetic and photoprotective pigments, flavonoids, organic acids, and carbohydrates are discussed. Finally, we propose that JD2 could be used together with bradyrhizobia to manipulate the chemical composition of plant tissues, promoting the nutritional benefits and health of soybean.

Rhizosphere modelling reveals spatiotemporal distribution of daidzein shaping soybean rhizosphere bacterial community

“…Enterobacteria that metabolize food-derived isoflavones have been reported to metabolize daidzein (Feng, Li, Oppong, & Qiu, 2018) Bradyrhizobium elkanii (Cagide, Riviezzi, Minteguiaga, Morel, & Castro-Sowinski, 2018), and Variovorax paradoxus, a soybean endophyte with characteristics related to plant growth promotion (Lopes, Carpentieri-Pipolo, Oro, Pagliosa, & Degrassi, 2016). Soil type primary influences the assemblage of rhizosphere microbial communities Xiao et al, 2017), and Comamonadaceae was abundant in the rhizosphere of successive soybean-monoculture cropping (Hamid et al, 2017), which is concordant with our findings using soils from soybean field under continuous cropping.…”

“…Comamonadaceae are common in the soybean rhizosphere (Hamid et al, ; White et al, ), with >10% relative abundance (Figure S9). This family contains plant growth promoting bacteria such as Delftia sp., which enhance nodulation and pulse yield when co‐inoculated with Bradyrhizobium elkanii (Cagide, Riviezzi, Minteguiaga, Morel, & Castro‐Sowinski, ), and Variovorax paradoxus , a soybean endophyte with characteristics related to plant growth promotion (Lopes, Carpentieri‐Pipolo, Oro, Pagliosa, & Degrassi, ). Soil type primary influences the assemblage of rhizosphere microbial communities (Liu et al, ; Xiao et al, ), and Comamonadaceae was abundant in the rhizosphere of successive soybean‐monoculture cropping (Hamid et al, ), which is concordant with our findings using soils from soybean field under continuous cropping.…”

Mechanisms in plant growth‐promoting rhizobacteria that enhance legume–rhizobial symbioses

“…The role of this gene in rhizobial infection or early steps of nodule development was also observed by Libault et al (2009). During nodule induction, the production of short fatty acids, such as caproic acid, which facilitates plant cell membrane fluidity and is essential for rhizobia colonization on the plant surface, was also increased when IAA-producing NER were used for co-inoculation (Brechenmacher et al 2010;Cagide et al 2018).…”

Bacterial Community Structure of Pinus Thunbergii Naturally Infected by the Nematode Bursaphelenchus Xylophilus

“…In the soil, only the genus Bradyrhzobium had a significantly higher abundance in diseased than healthy soil. The elevated soil pH in PWD-infested soil could be partly because Bradyrhzobium prefers acidic soils [66].…”