Improvement of rhizobium‐soybean symbiosis and nitrogen fixation under drought

Abstract

The symbiotic interaction between soybean plants and rhizobacteria can be severely affected by drought, which results in a reduction in symbiotic nitrogen fixation and ultimately decreased yields. The aim of our research was to determine whether symbiotically efficient rhizobia that can better tolerate soil water deficits can improve nodule performance in plants subjected to drought. Firstly, rhizobial strains were selected that exhibited differences in tolerance to salt (NaCl) or water deficit (PEG 6000). Sinorhizobium fredii strain SMH12 showed the highest tolerance to these treatments while Bradyrhizobium diazoefficiens strain WB74‐1 showed the lowest tolerance. Greenhouse‐grown Prima 2000 soybean plants were then inoculated with either SMH12 or WB74‐1 and subjected to two water deficit regimes. Different nodule and plant growth traits were determined, including nodule number, dry weight, water potential, and the accumulation of malondialdehyde and ureide. Plants inoculated with SMH12 had significantly more nodules under water deficit conditions than those inoculated WB74‐1, despite having lower root and shoot biomass. SMH12‐inoculated plants had higher nodule water potentials and lower malondialdehyde contents than the WB74‐1‐inoculated plants. These results demonstrate that inoculation of soybean plants with the more water deficit‐tolerant S. fredii strain improved nodule characteristics when plants were grown under water deficit conditions. However, these improved nodule characteristics do not always directly translate into better plant growth.

Enhanced Soybean Productivity by Inoculation With Indigenous Bradyrhizobium Strains in Agroecological Conditions of Northeast Germany

“…Thus, early drought and low temperature are important factors in regard to efficient N fixation and enhancement of soybean productivity traits. Other studies have reported induced nodule senescence, reduced leghemoglobin content, and BNF in leguminous plants grown under drought conditions compared with their counterparts in well-watered soils ( Ruiz-Lozano et al, 2001 ; Márquez-García et al, 2015 ; Kibido et al, 2020 ). As expected, the moisture regime influenced the shoot biomass increase but did not correspond with N uptake, likely as a result of the dilution effect due to the higher dry matter accumulation in the well-watered conditions ( Jarrell and Beverly, 1981 ).…”

“…The tolerance of rhizobium strains to drought reflects their ability to remain viable in the soil and is linked to the genetic traits that affect BNF, nodulation, survival, growth rate, and specificity with the host plant ( Zaman-Allah et al, 2007 ). Their efficiency in colonizing roots likely contributes to executing beneficial plant growth-promoting activities ( Kibido et al, 2020 ). On the other hand, the ability of the host plant to enhance BNF under drought conditions is linked to its sustained supply of photosynthates to the nodules ( King and Purcell, 2005 ).…”

Mapping quantitative trait loci related to nodule number in soybean (Glycine max (L.) Merr.) in response to the Sinorhizobium (Ensifer) fredii HH103 NopT type III effector

“…), which is one of the most important oil and protein crops worldwide, has evolved the ability to host N 2 -fixing bacteria (i.e. rhizobia) in specialized organs called root nodules (Kibido et al 2020;Liu et al 2020). Previous studies revealed that up to 90% of the seed nitrogen (N) content may be derived from N 2 fixation (Mastrodomenico and Purcell 2012).…”

Knockdown of GmD53a confers strigolactones mediated rhizobia interaction and promotes nodulation in soybean

“…Rhizobia-legume interaction also activates defense responses and increases salt tolerance in soybean seedlings ( Qu et al, 2016 ). In addition, under water deficit conditions, inoculation of rhizobia on soybean resulted in an increased number of nodules ( Kibido et al, 2020 ).…”