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

Abstract

Resumo -O objetivo deste trabalho foi avaliar o potencial de promoção do crescimento vegetal e a diversidade genética de bactérias isoladas de nódulos de feijão-caupi cultivado em solos do Cerrado piauiense. Avaliaram-se 26 estirpes quanto à capacidade de fixar nitrogênio em vida livre, solubilizar fosfatos inorgânicos, produzir ácido-3-indolacético (AIA) na ausência e na presença do aminoácido triptofano (100 mg L -1 ), produzir nódulos e promover o crescimento de feijão-caupi em vasos Leonard. Nenhuma estirpe fixou nitrogênio em vida livre, e 69% foram capazes de solubilizar fosfato de cálcio in vitro. Na presença de triptofano, todas as estirpes foram capazes de sintetizar o AIA em meio 79, e 80% sintetizaram o AIA em meio DYGS. Apenas quatro estirpes nodularam o feijão-caupi. O sequenciamento do gene 16S rRNA identificou as estirpes nodulíferas como pertencentes aos gêneros Bradyrhizobium, Rhizobium, Bacillus e Paenibacillus. Entre as estirpes não nodulíferas promotoras do crescimento do feijão-caupi, estão os gêneros Bacillus e Paenibacillus.Termos para indexação: ácido-3-indolacético, fixação biológica de nitrogênio, solubilização de fosfatos. Plant growth promotion and genetic diversity of bacteria isolated from cowpea nodulesAbstract -The objective of this work was to evaluate the potential for plant growth promotion and the genetic diversity of bacteria isolated from nodules of cowpea grown in Cerrado soils in the state of Piauí, Brazil. Twenty-six strains were evaluated as to their ability to fixate free-living nitrogen, solubilize inorganic phosphates, produce indole-3-acetic acid (IAA) in the absence and presence of tryptophan (100 mg L -1 ), produce nodules, and promote cowpea growth in Leonard jars. No strain was able to fixate free-living nitrogen, and 69% were able to solubilize calcium phosphate in vitro. In the presence of tryptophan, all strains were able to synthesize IAA in the 79 medium, and 80% synthesized IAA in the DYGS medium. Only four strains nodulated cowpea. The sequencing of the 16S rRNA gene identified the nodulating strains as belonging to the genera Bradyrhizobium, Rhizobium, Bacillus, and Paenibacillus. Among the non-nodulating strains able to promote cowpea growth are the genera Bacillus and Paenibacillus.

Cowpea Nodules Harbor Non-rhizobial Bacterial Communities that Are Shaped by Soil Type Rather than Plant Genotype

“…In Brazil, where cowpea is an introduced species, a higher diversity of bacteria associated to the nodules has been described (Martins et al, 1997; Leite et al, 2009). Bacterial strains assigned to the phylum Firmicutes (genera Bacillus and Paenibacillus ) were obtained from root nodules of cowpea plants cultivated in Brazilian semi-arid soils (Costa et al, 2013). Particularly for the Amazonian region, a number of strains classified as Pseudomonas, Enterobacter (Gammaproteobacteria), Bacillus , and Paenibacillus were isolated from cowpea nodules (Jaramillo et al, 2013; Oliveira-Longatti et al, 2014).…”

“…This evidence also indicates that Chryseobacterium is an established member of the bacterial community in the BEF soils. Several studies already isolated other NRE from cowpea nodules belonging to Proteobacteria, Firmicutes, and Actinobacteria phyla (Guimarães et al, 2012; Costa et al, 2013; Jaramillo et al, 2013) using standard media for rhizobial isolation. Nevertheless, Bacteroidetes, such as Chryseobacterium , were not obtained up to now, probably because the great part of environmental isolates from this genus are not able to metabolize mannitol (Cho et al, 2010), the carbon source preferred by rhizobia.…”

Estirpes de Bradyrhizobium em simbiose com guandu-anão em casa de vegetação e no campo

“…A maioria das estirpes de BFNN, aprovadas para espécies florestais, adubo verde, forrageiras e para grãos, pertence a esse gênero, e muitas já são usadas com sucesso há décadas, sem a perda de suas propriedades simbióticas, como as de soja e de feijão-caupi. Para uso com feijão-caupi, têm sido relatadas novas estirpes eficientes de Bradyrhizobium (Guimarães et al, 2012;Costa et al, 2013;Jaramillo et al, 2013), o que pode ser extrapolado também para guandu.…”

<b>Symbiosis of rhizobia with <i>Gliricidia sepium </i> and <i>Clitoria fairchildiana</i> in an Oxisol in the pre-Amazon region of Maranhão State

“…Partial amplification parameters, primer sequences, cycle conditions, and sequencing protocol of the 16S rRNA gene were previously described by Costa et al (2013). The quality of the sequences was analysed with the BioNumerics 7.1 software (Applied Maths, Austin, TX, USA).…”

“…Studies have demonstrated that strains of the Bacillus genus can coexist with Bradyrhizobium in nodules and can nodulate and biologically fix nitrogen (Li, Wang, Chen, & Chen, 2008;Costa et al, 2013). It has been demonstrated that bacteria belonging to the Arthrobacter and Klebsiella genera are found in the rhizosphere in association with roots, or live freely in the soil, and promote plant growth (Kloepper, Lifshitz, & Zablotowicz, 1989;Glick, 1995).…”