02839naa a2200361 a 450000100080000000500110000800800410001910000220006024501290008226000090021152018860022065000110210665000120211765000170212965000090214665000130215565000160216865000280218465000210221265000160223365000120224965000140226165000090227565000090228465300110229365300100230465300150231465300110232965300200234070000200236070000200238077300770240016210961999-06-14       1997    bl uuuu     u00u1 u    #d1 aMARTINS, L. M. V.  aGrowth characteristics and symbiotic efficiency of rhizobia isolated from cowpea nodules of the North-East region of Brazil.  c1997  aIn Brazil, the geo-environmental conditions of the north-east region exert an effect on the rhizobia diversity. A large collection of rhizobia isolates were obtained from nodules of cowpea planted in different soils from this region of Brazil. Cowpea was selected as the scavenger for this study of rhizobia diversity because it is a known broad host-range leguminous plant and it is also widespread in the region. A total of 536 nodule isolates were obtained and later arranged in 78 different groups based on colony morphology and growth. Growth in culture media of isolate representatives of these groups revealed that 27 of them showed fast growth characteristics although the plant is characteristically nodulated by strains described as Bradyrhizobium spp. Furthermore, the analysis of the isolates from each region showed an increased proportion of fast-growing rhizobia when going from the coast to the semi-arid region. Fifty-five of the rhizobia representatives from the Brazilian north-east region induced Hup+ phenotype in cowpea nodules indicating the predominance of this phenotype. They were also inoculated into soybean, since this legume plant is nodulated by the slow-growing rhizobia species B. japonicum and B. elkanii. Twenty-five of the group representatives were not capable of nodulating soybean. Inoculation with some of them promoted the formation of pseudo-nodule structures which despite not contributing significantly to the nitrogen content of the plant are an indication that signal exchange between plant and rhizobia is occurring. The remaining isolate representatives were capable of nodulating soybean. The nodulation of soybean by the isolates in soils of the semi-arid region of Brazil is quite remarkable since this crop has never been cultivated in the region before. Data on host-regulated uptake hydrogenase phenotype (Hup-hr) is discussed.  aBrazil  acowpeas  aroot nodules  asoil  asoybeans  aCrescimento  aEficiência Nutricional  aFeijão de Corda  aNodulação  aNódulo  aRhizobium  aSoja  aSolo  aBrasil  aCaupi  aEfficiency  aGrowth  aRoot nodulation1 aNEVES, M. C. P.1 aRUMJANEK, N. G.  tSoil Biology and Biochemistry, Oxfordgv. 29, n. 5/6, p.1005-1010, 1997.