Peanut (Arachis hypogaea L.) is capable of establishing an efficient symbiosis with a wide range of rhizobia, nevertheless, the inoculation of this legume is under used due to lack of information on the bacteria naturally established in soils and the agronomic and economic viability of the practice. The aim of this study was to evaluate the diversity and the symbiotic efficiency of peanut rhizobia from a Planosol under different vegetation covers (native vegetation, sugarcane cultivation and fallow after sugarcane cultivation), located in Zona da Mata, Northeast of Brazil. A total of 177 isolates were obtained from peanut nodules, most of them having the characteristic of rapid growth and acidification of the Yeast Mannitol Agar (YMA) medium. The isolates obtained from soil samples with native vegetation cover showed higher relative abundance, higher species richness and greater uniformity of morphological groups of rhizobia. Eighteen isolates were evaluated for their ability to nodulate peanuts, of which 13 have been authenticated and submitted to evaluation of symbiotic efficiency in pots with soil. The isolate 23M showed the best symbiotic performance in pots with soil. In the field, plants inoculated with the isolate 23M showed better performance than non-inoculated plants, in addition to a grain yield (kg ha-1) similar to that of plants inoculated with recommended bacteria or receiving 200 kg ha-1 N.
Key words: Bacteria of legume nodules, biological nitrogen fixation, diversity, grain legume, sugarcane field reform.
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