Biodiversity of rhizobia associated with cowpea cultivars in soils of the lower half of the São Francisco River Valley

Revista Brasileira de Ciência do Solo

Jakson Leite²  Sirando Lima Seido¹  Samuel Ribeiro Passos²  Gustavo Ribeiro Xavier¹  Norma Gouvêa Rumjanek¹  Lindete Míria Vieira Martins¹ 

[1] ,Universidade Federal Rural do Rio de Janeiro Departamento de Agronomia e Ciência do Solo Seropédica RJ

关键词: ARDRA;    biological nitrogen fixation;    Vigna unguiculata;    ARDRA;    fixação biológica de nitrogênio;    Vigna unguiculata;   

DOI  :  10.1590/S0100-06832009000500015

来源: SciELO

【 摘 要 】

The biodiversity of rhizobium in soils of the São Francisco Valley is unknown and can be studied using cowpea as trap plants. The objective of this study was to verify the diversity of diazotrophic bacteria that nodulate cowpea in soils of the lower half of the São Francisco River Valley by morphological and genotypic characterization. Seven soil samples (A1, A2, A3, A4, C1, C2 and MC) were collected to capture bacteria associated to five cowpea cultivars (IPA 206, BRS Pujante, BRS Marataoã, Canapu Roxo, and Sempre Verde), in a 5x7 factorial design with three replications. Thirty days after plant emergence, the nodules were collected and the bacteria isolated and analyzed in relation to their growth characteristics in YMA medium. The 581 isolates were grouped in 49 morphologic groups. Of this total, 62.3 % formed colonies in up to three days, 33.4 % grew from the 6th day on, and 4.3 % began to grow 4 to 5 days after incubation. Regarding the formation of acids and alkalis, 63 % acidified the medium, 12 % made it alkaline and 25 % maintained the medium at neutral pH. The highest diversity was observed in the A3 sample and in isolates associated with the cultivars Canapu Roxo and BRS Pujante. Thirty-eight representative isolates were chosen for the genotypic characterization, clustered in four groups based on the restriction analysis of 16s rDNA. This grouping was strongly correlated with the sampling site; 13 rhizobium isolates had an electrophoretic profile distinct from the standard rhizobium strains used in this study.

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