Phenotypic and molecular characteristics of rhizobia isolated from nodules of peanut (Arachis hypogaea L.) grown in Brazilian Spodosols

Abstract

Peanut (Arachis hypogaea L.) is an important crop that can fix nitrogen through symbiosis with rhizobia. Rhizobia populations with diverse characteristics than those traditionally described as peanut microsymbionts have been found in tropical soils. With the objective of studying the diversity and phylogeny of these rhizobia, 22 bacterial strains were isolated from nodules of seven peanut varieties grown in Spodosols of Pernambuco State, Brazil. The isolates were examined in culture medium by means of some of their phenotypic characteristics and tested for intrinsic antibiotic resistance (IAR). DNA profiles were determined with the BOX-PCR and compared with 19 reference strains. All isolates showed rapid growth, and most of them acidified the culture medium. In general, high antibiotic resistance was observed to penicillin G, chloramphenicol and tetracycline and susceptibility was observed to neomycin, erythromycin and rifampicin. The analysis of their phenotypic characteristics, that is, colony morphology and IAR, provided little information about the phylogeny of the isolates. However, using compilation of phenotypic and molecular characteristics, we were able to observe a great diversity of these rhizobia and to reveal the presence of new species.

Diversity of new root nodule bacteria from Erythrina velutina Willd., a native legume from the Caatinga dry forest (Northeastern Brazil)

“…Among the cultivated species, studies conducted in Brazil have already examined the genetic variability of rhizobia of legumes such as pigeonpea (Costa et al, 2014), peanuts (Lyra et al, 2013;TorresJúnior et al, 2014), common beans (Stocco et al, 2008), among others. This technique is also used to examine the variability of strains isolated from native plants such as bromeliad (Giongo et al, 2013), wild rice (Fernandes Júnior et al, 2013) and legumes (Granada et al, 2014).…”

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

“…Whether because nodule formation in groundnut is by crack entry and infection thread invasion (Tajima et al, 2008), groundnut-nodulating symbionts tend to reveal high levels of diversity and heterogeneity when obtained from different regions of Africa. This heterogeneity could be due to the high level of promiscuity reported for groundnut nodulation (Nievas et al, 2012; Jaiswal et al, 2017; Osei et al, 2018) as it can form effective symbiosis with both slow- and fast-growing bacteria belonging to the genera Rhizobium and Bradyrhizobium in African soils (Taurian et al, 2006; El-Akhal et al, 2008; de Freitas and Silva, 2013; Jaiswal et al, 2017; Osei et al, 2018). The fast-growing rhizobia that are reported to effectively nodulate groundnut in African soils, include R. giardinii and R. tropici (Taurian et al, 2006; Jaiswal et al, 2017; Osei et al, 2018).…”

Can Bradyrhizobium strains inoculation reduce water deficit effects on peanuts?

“…Peanut is able to associate efficiently with different rhizobial strains (Melo et al 2016), presenting higher efficiency the Bradyrhizobium genus (Valetti et al 2016;Santos et al 2017a). During the last years, some studies have been carried out in Brazil aiming to evaluate the biodiversity (Lyra et al 2013;Torres-Júnior et al 2014;Santos et al 2017a), the symbiotic efficiency (Torres-Júnior et al 2014;Santos et al 2017a, b), and the agronomic efficiency of new rhizobium strains (Sizenando et al 2016). However, the potential of these bacteria to reduce the abiotic stresses, as water deficit, for example, has not been investigated.…”