African origin of Bradyrhizobium populations nodulating Bambara groundnut (Vigna subterranea L. Verdc) in Ghanaian and South African soils

Abstract

Flavonoids secreted by legumes play a major role as signal molecules for attracting compatible rhizobia. The aim of this study was to assess and understand the diversity of microsymbionts nodulating Bambara groundnut (Vigna subterranea L. Verdc.) landraces of different seedcoat colours using restriction fragment length polymorphism and phylogenetic analysis. Seedcoat pigmentation of landraces had effect on the diversity of microsymbionts of Bambara groundnut. Even when planted together in one hole, nodulating bradyrhizobia clustered differently. For example, 16S rDNA-RFLP typing of rhizobial samples TUTVSBLM.I, TUTVSCRM.I and TUTVSRDM.I originating respectively from Black, Cream and Red landraces that were co-planted in the same hole at Manga in the Sudano-sahelian savanna, as well as TUTVSCRK.I and TUTVSRDK.I respectively from Cream and Red landraces co-planted at Kpalisogu in the Guinea savanna, revealed different 16S rDNA- RFLP types. Phylogenetic analysis of 16S rDNA, glnII, recA and atpD sequences showed that Vigna subterranea was nodulated specifically by a diverse group of Bradyrhizobium species (e.g. Bradyrhizobium vignae, and a novel group of Bradyrhizobium spp.) in soils from Ghana and South Africa. The recA gene phylogeny showed incongruency with the other housekeeping genes, indicating the possibility of lateral gene transfer and/or recombination events. The grouping of isolates according to symbiotic gene (nifH and nodD) phylogenies revealed inter- and intra-specific symbiotic plasmid transfer and different evolutionary history. The results also showed that a cropping history and physico-chemical environment of soils increased bradyrhizobial diversity in Ghana and South Africa.

Impact of <i>Cowpea mottle virus</i> on the Growth and Yield of Bambara Groundnut (<i>Vigna subterranean</i> (L.) Verdc.)

“…The crop is adapted to various climatic and ecological conditions and fits well with the semi-arid climatic condition of the country. As a leguminous plant, it contributes to soil fertilization through the symbiotic fixation of atmospheric nitrogen [1] [2] [3]. Moreover, Burkina Faso is one of the main producers and exporters of bambara groundnut in West Africa.…”

Identification and distribution of microsymbionts associated with soybean nodulation in Mozambican soils

“…The phylogenetic analysis of individual housekeeping genes also suggested that most of the isolates were highly aligned with B. elkanii . However, the phylogenetic positions of isolates TUTDAIAP3B, TUTDAIAP8B and TUTMCJ5B were not stable in single gene phylogenies, and this could suggest recombination, migration or horizontal gene transfer [8] , [36] .…”

Diversity of Bradyrhizobia in Subsahara Africa: A Rich Resource

“…To date, only a small number of surveys used MLSA to uncover the microsymbiont diversity in SSA. The few studies focusing on “cowpea group” rhizobia (from agricultural plants) spanned the countries of Botswana and South Africa (Steenkamp et al, 2008 ), Botswana, South Africa, and Ghana (Pule-Meulenberg et al, 2010 ), Senegal (Wade et al, 2014 ), Namibia and Angola (Grönemeyer et al, 2014 ), Ghana and South Africa (Puozaa et al, 2017 ), Mozambique (Chidebe et al, 2018 ), Kenya (Ndungu et al, 2018 ), and Ethiopia (Degefu et al, 2018 ). Their main findings were in general agreement: First, almost all detected genotypes presumably represented yet unknown species (Steenkamp et al, 2008 ; Grönemeyer et al, 2014 ; Wade et al, 2014 ; Degefu et al, 2018 ).…”

“… Maximum likelihood-based phylogeny inferred from glnII-recA sequences of SSA bradyrhizobia and species type strains. SSA isolates from agricultural plants (see legend) obtained in five African studies are represented (Steenkamp et al, 2008 ; Grönemeyer et al, 2014 ; Wade et al, 2014 ; Puozaa et al, 2017 ; Chidebe et al, 2018 ). Considerably shorter sequences were excluded, and representatives were selected for identical sequences.…”

“…Apart from the geographic location, this observation might be related to the natural selectivity of the sampled legume hosts and the lack of taxonomic studies. Relatively few studies focused on natural microsymbionts of cowpea and especially Bambara groundnut (Pule-Meulenberg, 2014 ; Puozaa et al, 2017 ). The first validly published species from this host, B. subterraneum (Grönemeyer et al, 2015a ) was mainly isolated from Bambara groundnut, and also from peanut.…”