Genetic and Symbiotic Diversity of Nitrogen-Fixing Bacteria Isolated from Agricultural Soils in the Western Amazon by Using Cowpea as the Trap Plant

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Cowpea is a legume of great agronomic importance that establishes symbiotic relationships with nitrogen-fixing bacteria. However, little is known about the genetic and symbiotic diversity of these bacteria in distinct ecosystems. Our study evaluated the genetic diversity and symbiotic efficiencies of 119 bacterial strains isolated from agriculture soils in the western Amazon using cowpea as a trap plant. These strains were clustered into 11 cultural groups according to growth rate and pH. The 57 nonnodulating strains were predominantly fast growing and acidifying, indicating a high incidence of endophytic strains in the nodules. The other 62 strains, authenticated as nodulating bacteria, exhibited various symbiotic efficiencies, with 68% of strains promoting a significant increase in shoot dry matter of cowpea compared with the control with no inoculation and low levels of mineral nitrogen. Fifty genotypes with 70% similarity and 21 genotypes with 30% similarity were obtained through repetitive DNA sequence (BOX element)-based PCR (BOX-PCR) clustering. The 16S rRNA gene sequencing of strains representative of BOX-PCR clusters showed a predominance of bacteria from the genus<jats:named-content content-type="genus-species">Bradyrhizobium</jats:named-content>but with high species diversity.<jats:named-content content-type="genus-species">Rhizobium</jats:named-content>,<jats:named-content content-type="genus-species">Burkholderia</jats:named-content>, and<jats:named-content content-type="genus-species">Achromobacter</jats:named-content>species were also identified. These results support observations of cowpea promiscuity and demonstrate the high symbiotic and genetic diversity of rhizobia species in areas under cultivation in the western Amazon.</jats:p>

Legume Nodulating Bacterium, Achromobacter xylosoxidans Found in Tropical Shrub Agroecosystem, Sumatera, Indonesia

“…This bacterium is one of the genera belonging to betaproteobacteria, which have been reported as legume nodulating bacteria for the fi rst time by Benata et al (2008). A. xylosoxidans formed root nodule in Prosopis julifl ora (Benata et al, 2008); Mucuna bracteata (Salwani et al, 2012); and cowpea (Guimarães et al, 2012). In this study, we also confi rmed the existence of nifH and nodA copy genes.…”

“…40 days after cultivation of soybean, observation showed that UGM48a formed nodule (Table 3). A. xylosoxidans has previously been reported having ability to nodulate Prosopis julifora (Benata et al, 2008); cowpea (Guimarães et al, 2012); and Mucuna bracteata (Salwani et al, 2012). This is the fi rst fi ndings that A. xylosoxidans were able to nodulate soybean.…”

Promoção do crescimento vegetal e diversidade genética de bactérias isoladas de nódulos de feijão-caupi

“…é uma leguminosa de grande importância agrícola, por ser uma das principais fontes de proteína vegetal e contribuir de forma significativa para a geração de renda no campo, nas regiões Norte e Nordeste do Brasil. Essa espécie é capaz de beneficiar-se amplamente da FBN e tem sido bastante utilizada como planta-isca em estudos de diversidade de BFNNL, em razão da sua capacidade de formar simbiose com diversos gêneros e espécies de bactérias (Moreira, 2006;Guimarães et al, 2012). Além disso, foi relatado o isolamento de bactérias não simbióticas, em nódulos de feijão-caupi, com grande potencial de promoção do crescimento vegetal (Marra et al, 2012).…”

“…bras., Brasília, v.48, n.9, p.1275-1284, set. 2013 DOI: 10.1590/S0100-204X2013000900012 a identificação de estirpes pertencentes aos gêneros Bradyrhizobium e Rhizobium, provenientes de nódulos de feijão-caupi (Guimarães et al, 2012;Jaramillo et al, 2013). Contudo, os gêneros Paenibacillus e Bacillus geralmente são endofíticos de nódulos, mas não nodulíferos, embora haja relatos da nodulação em feijão-caupi por esses dois gêneros (Marra et al, 2012;Jaramillo et al, 2013).…”

“…Diante disto, têm sido realizados estudos da diversidade dessas bactérias (Zilli et al, 2004;Moreira, 2006;Guimarães et al, 2012), de suas relações ecológicas e da seleção de estirpes eficientes (Lima et al, 2005), com vistas à região também são adaptadas a condições de estresse, como altas temperaturas.…”