Selection of Bradyrhizobium or Ensifer symbionts by the native Indian caesalpinioid legume Chamaecrista pumila depends on soil pH and other edaphic and climatic factors

Abstract

Nodules of Chamaecrista pumila growing in several locations in India were sampled for anatomical studies and for characterization of their rhizobial microsymbionts. Regardless of their region of origin, the nodules were indeterminate with their bacteroids contained within symbiosomes which were surrounded by pectin. More than 150 strains were isolated from alkaline soils from the Thar Desert (Rajasthan), wet-acidic soils of Shillong (Meghalaya), and from trap experiments using soils from four other states with different agro-ecological regions. Molecular phylogenetic analysis based on five housekeeping (rrs, recA, glnII, dnaK andatpD) and two symbiotic (nodA and nifH) genes was performed for selected strains. Chamaecrista pumila was shown to be nodulated by niche-specific diverse strains of either Ensifer or Bradyrhizobium in alkaline (Thar Desert) to neutral (Tamil Nadu) soils and only Bradyrhizobium strains in acidic (Shillong) soils. Concatenated core gene phylogenies showed four novel Ensifer-MLSA types and nine Bradyrhizobium-MLSA types. Genetically diverse Ensifer strains harbored similar sym genes which were novel. In contrast, significant symbiotic diversity was observed in the Bradyrhizobium strains. The C. pumila strains cross-nodulated Vigna radiata and some wild papilionoid and mimosoid legumes. It is suggested that soil pH and moisture level played important roles in structuring the C. pumila microsymbiont community.

Impact of a <i>G2-EPSPS</i> & <i>GAT</i> Dual Transgenic Glyphosate-Resistant Soybean Line on the Soil Microbial Community under Field Conditions Affected by Glyphosate Application

“…As shown in Fig. 3, the proportional contribution of E. fredii was higher in root samples at the flowering stage of ZH10 and Z106J than that of Z106, which is reported to be involved in nitrogenfixing nodule formation in plants and is a very common symbiont of soybean (Temprano-Vera et al, 2018) and other legumes (Rathi et al, 2018) in alkaline soils, in which it forms determinate nodules in soybean and cowpea (Krishnan, 2002;Lopez-Baena et al, 2016). Furthermore, E. fredii is a fast-growing root nodule bacterium with a broad spectrum of hosts that was initially isolated from Chinese soil and nodulates the roots of 79 diverse genera of legumes (Krishnan, 2002;Albareda et al, 2009).…”

Sinorhizobium fredii Strains HH103 and NGR234 Form Nitrogen Fixing Nodules With Diverse Wild Soybeans (Glycine soja) From Central China but Are Ineffective on Northern China Accessions

“…The central province of Shaanxi was not included in this study. Recent work from India also suggests that Bradyrhizobium strains are very abundant as nodulators of a number of native legumes in acidic soils, whereas Sinorhizobium are more prevalent in neutral-alkaline soils ( Ojha et al, 2017 ; Sankhla et al, 2017 ; Rathi et al, 2018 ).…”

“…Thus, soil pH appears to be a decisive criterion in determining whether fast- or slow-growing soybean rhizobia communities will populate fields, including soils from alkaline spots of otherwise acidic soils of Honghu county (Hubei province) where S. fredii populations were found to be predominant ( Camacho et al, 2002 ). In fact, sinorhizobial strains are often associated with legumes that are native to alkaline soils, not only in China but also in other countries such as India ( Sankhla et al, 2017 ; Rathi et al, 2018 ).…”

Widespread Distribution of Highly Adapted Bradyrhizobium Species Nodulating Diverse Legumes in Africa

“…Of these, only ten ( B. algerianse, B. cytisi, B. kavangense, B. namibiense, B. subterraneum, B. retamae, B. rifense, B. ripae, B. vignae , and B. shewense ) have an African origin with an ability to tolerate acidic to alkaline conditions (pH 4–9) (Chahboune et al, 2011; Chahboune et al, 2012; Guerrouj et al, 2013; Grönemeyer et al, 2015a,b, 2016, 2017; Ahnia et al, 2018; Bünger et al, 2018) (see Table 1). It therefore appears that the physico-chemical properties of soils play an important role in influencing the diversity of bradyrhizobial community in a niche (Jaiswal et al, 2016; Ojha et al, 2017; Puozaa et al, 2017; Rathi et al, 2018).…”