Resumo

GOMEZ-PADILLA, Ernesto et al. Characterization of rhizobia isolated from cowpea nodules, in Cuban saline soils. cultrop [online]. 2017, vol.38, n.4, pp.39-49. ISSN 0258-5936.

In soils of Cauto River Valley (Granma, Cuba) affected by salts, six new bacteria isolated from nodules of Vigna unguiculata (L.) Walp were obtained. The six isolates were subjected to differents salt levels (0,17- 6,6 dS m^-1 of NaCl), pH levels (4,5 - 9) and temperatures (28 - 45 ^oC) with the objective to determine their tolerance to these abiotic stresses. Variation within the 16S rRNA gene, was examined by amplified 16S rDNA restriction analysis (ARDRA) and direct sequencing to show genetic diversity. Three isolates (VIBA-1, VIBA-2 and VIBA-6) achieved similar results as the control with 2,6 and 3,4 dS m^-1 of NaCl. All of the isolates could grow at pH 7 and 9 and got growth until 40 ^oC, only two of them (VIBA-4 and VIBA-5) grew at 45 ^oC. Phylogeny analysis confirmed the close relationship of one isolate with Bradyrhizobium liaoningense (VIBA-1) and four isolates with Bradyrhizobium yuanmingense (VIBA-2, VIBA-3, VIBA-5 and VIBA-6) and one to Rhizobium radiobacter (formely Agrobacterium tumefaciens, VIBA-4). All of them, with the exception of VIBA-4, were able to nodulate in the plants when they were inoculated. The survival of these strains in the different abiotic stress (salinity, alkalinity and temperature), evidenced their ability to grow under this specific environment. The findings indicated that under Cuban saline soils there are Bradyrhizobium strains able to establish symbiosis with cowpea, but the diversity is still low, being characterized only two different species able to nodulate

Palavras-chave : Bradyrhizobium sp; molecular identification; nodulation; salinity; tolerance; Vigna unguiculata.

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