Eco-geographical diversity of cowpea bradyrhizobia in Senegal is marked by dominance of two genetic types
La diversité éco-géographique des bradyrhizobia du niébé au Sénégal est marquée par la dominance de deux types génétiques
Krasova Wade, T. ; Le Quéré, A. ; Laguerre, G. ; N'Zoué, A. ; Ndione, J.A. ; Do Rego, F. ; Sadio, O. ; Ndoye, I. ; Neyra, M.
Type de document
Article de revue scientifique à comité de lecture
Affiliation de l'auteur
IRD DAKAR SEN ; IRD UMR113 MONTPELLIER FRA ; INRA UMR113 MONTPELLIER FRA ; IRD UMR113 MONTPELLIER FRA ; CENTRE DE SUIVI ECOLOGIQUE DAKAR SEN ; IRD DAKAR SEN ; IRD DAKAR SEN ; UNIVERSITE CHEIKH ANTA DIOP UCAD LABORATOIRE COMMUN DE MICROBIOLOGIE IRD-ISRA-UCAD DAKAR SEN ; IRSTEA LYON UR MALY FRA
Résumé / Abstract
The genetic diversity of native cowpea rhizobia originating from 60 sites across four eco-geographic zonesin Senegal was studied. More than 300 cowpea nodules were analyzed by PCR-RFLP of the 16S–23S rDNAInterGenic Spacer region (IGS). Alignments of IGS sequences indicated that all genotypes were groupingwithin the Bradyrhizobium genus. The geographical distribution showed that apart from five IGS types,the others were specifically found in only one region. The diversity was significantly higher in the SenegalRiver valley zone, which presents lower mean annual rainfalls and slightly alkaline soils. Interestingly,two IGS types dominated the Senegalese rhizobial collection, one IGS type (VI) was found on more thanhalf of the nodules collected in the northern Senegal River valley while another IGS type (I) was recoveredfrom the great majority of nodules in the three other regions sampled. Two representative strains fromeach of these two dominant types were isolated and further analyzed. Multi Locus Sequence Analysesusing 6 housekeeping genes indicate that they belong to a new Bradyrhizobium species closely related toB. yuanmingense. Phylogenetic analyses of 2 symbiotic genes nodC and nifH show that they are clusteredwith B. arachidis. Physiological tests on these strains have shown that under laboratory conditions, thegrowth of the IGS type VI strains was slightly less affected by a higher osmotic strength in the mediumand to alkaline pH, which corroborates the soil physico-chemical parameters.
Systematic and Applied Microbiology, vol. 37, p. 129 - 139