Total DNA was extracted and amplified from 202 crushed nodules. All yielded single IGS PCR products ranging from 910 pb to 1035 pb. After digestion with restriction enzymes HaeIII and Mspl, 202 profiles were organized into nine distinct restriction patterns, named IGS types I to IX.
The IGS sequence analysis of the nine patterns showed that the strains belong to the Bradyrhizobium genus. IGS types II, III, IV and VIII are closely related to some strains isolated from Faidherbia albida in Senegal (Dupuy et al. 1992). IGS types III and IV could be grouped within Bradyrhizobium genospecies VII of Willems et al. (2001), corresponding to Bradyrhizobium japonicum species. IGS type II and VIII showed more than 96% similarity with genospecies IV. The five other IGS types, with lower IGS similarity, could correspond to new genospecies.
The IGS type I was found in 175 nodules collected through all prospected sites. The IGS types II, III and VIII were found in more than one site, located in the Center-North and the Southeast for the IGS type II and VIII, and in the Center-North and the North for the IGS type III. The five other IGS types were revealed only once, in sites grouped principally in the Center-North. However, due to the low frequency at which strains from IGS types II to IX are found, no clear relationship could be determined between the geographical origins of strains and their grouping by IGS sequence analysis.
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