Phylogenetic Analysis of Symbiotic Bacteria Associated with Two <i>Vigna</i> Species under Different Agro-Ecological Conditions in Venezuela

Abstract

Vigna is a genus of legumes cultivated in specific areas of tropical countries. Species in this genus are important crops worldwide. Vigna species are of great agronomic interest in Venezuela because Vigna beans are an excellent alternative to other legumes. However, this type of crop has some cultivation issues due to sensitivity to acidic soils, high temperatures, and salinity stress, which are common in Venezuela. Vigna species establish symbioses mainly with Bradyrhizobium and Ensifer, and Vigna-rhizobia interactions have been examined in Asia, Africa, and America. However, the identities of the rhizobia associated with V. radiata and V. unguiculata in Venezuela remain unknown. In the present study, we isolated Venezuelan symbiotic rhizobia associated with Vigna species from soils with contrasting agroecosystems or from fields in Venezuela. Several types of soils were used for bacterial isolation and nodules were sampled from environments characterized by abiotic stressors, such as high temperatures, high concentrations of NaCl, and acidic or alkaline pH. Venezuelan Vigna-rhizobia were mainly fast-growing. Sequencing of several housekeeping genes showed that in contrast to other continents, Venezuelan Vigna species were nodulated by rhizobia genus including Burkholderia, containing bacteria from several new phylogenetic lineages within the genus Bradyrhizobium. Some Rhizobium and Bradyrhizobium isolates were tolerant of high salinity and Al toxicity. The stress tolerance of strains was dependent on the type of rhizobia, soil origin, and cultivation history. An isolate classified as R. phaseoli showed the highest plant biomass, nitrogen fixation, and excellent abiotic stress response, suggesting a novel promising inoculant for Vigna cultivation in Venezuela.

Bradyrhizobium as the Only Rhizobial Inhabitant of Mung Bean (Vigna radiata) Nodules in Tropical Soils: A Strategy Based on Microbiome for Improving Biological Nitrogen Fixation Using Bio-Products

“…In another study, Mesorhizobium OTUs were not found, while Rhizobium corresponded to only 0.8% of the total sequences analyzed ( Hakim et al, 2020 ). In a study conducted in Venezuela, Rhizobium strains have been isolated from mung bean nodules ( Ramírez et al, 2020 ). In this sense, the absence of OTUs from Ensifer , Rhizobium , and Mesorhizobium genera in our study could be related to either a PCR bias caused by the low concentration of these organisms, or a possible allocation of these OTUs as unclassified groups ( Lee et al, 2012 ; Van Dijk et al, 2014 ).…”

Co-inoculation of two symbiotically efficient Bradyrhizobium strains improves cowpea development better than a single bacterium application

“…Among the 35 bacteria assessed in this study, 34 belong to the B. japonicum genomic superclade (Oliveira et al 2020;Sena et al 2020), contrasting to the taxonomic position of B. pachyrhizi BR 3262 in the B. elkanii superclade. The biodiversity studies of cowpea in Brazil (Silva et al 2012;Guimarães et al 2015;Oliveira et al 2020;Sena et al 2020), Venezuela (Ramirez et al 2020), and the African continent (Mohammed et al 2018;Jaiswal and Dakora 2019) indicated the preference of cowpea to nodulate with the B. japonicum-like bradyrhizobia in the tropics, what probably influenced in the nodule occupancy of BR 3262.…”

Biodiversity and Geographic Distribution of Rhizobia Nodulating With Vigna minima

“…Species within the genus include essential and valuable crop plants such as Vigna unguiculata (L.) Walp. and Vigna radiata (L.) R. Wilczek and are cultivated mainly in Asian countries with approximately 11 million hectares ( Ramírez et al, 2020 ). However, a number of wild species, such as Vigna minima (Roxb.…”

“…As typical legume members, the cultured Vigna species could nodulate with diverse rhizobial species ( Ramírez et al, 2020 ), but mainly the Bradyrhizobium species. The mung bean ( Vigna radiata L.) plants mainly nodulate with Bradyrhizobium japonicum , Bradyrhizobium liaoningense , Bradyrhizobium yuanmingense , and Bradyrhizobium elkanii and rarely with members of the genera Ensifer , Rhizobium , and Mesorhizobium ( Yang et al, 2008 ; Zhang et al, 2008 ; Risal et al, 2012 ; Hakim et al, 2018 ).…”