Bacterial strains from floodplain soils perform different plant-growth promoting processes and enhance cowpea growth

Abstract

Certain nodulating nitrogen-fixing bacteria in legumes and other nodule endophytes perform different plant-growth promoting processes. The objective of this study was to evaluate 26 bacterial strains isolated from cowpea nodules grown in floodplain soils in the Brazilian savannas, regarding performance of plant-growth promoting processes and ability to enhance cowpea growth. We also identified these strains by 16S rRNA sequencing. The following processes were evaluated: free-living biological nitrogen fixation (BNF), solubilization of calcium, aluminum and iron phosphates and production of indole-3-acetic acid (IAA). The abilities to nodulate and pro- ) were obtained in the 79 medium with tryptophan by Enterobacter strains UFPI B5-7A, UFPI B5-4 and UFPI B5-6, respectively. Only eight strains nodulated cowpea, however, all increased production of total dry matter. The fact that the strains evaluated perform different biological processes to promote plant growth indicates that these strains have potential use in agricultural crops to increase production and environmental sustainability.

Plant growth‐promoting rhizobacterial communities from an area under the influence of iron mining and from the adjacent phytophysiognomies which have high genetic diversity

“…(Armanhi et al, 2018;Cao et al, 2015;Castro et al, 2017;Chou et al, 2007;De Meyer et al, 2015;Hoque et al, 2011;Li et al, 2011;Lu et al, 2017;Sun et al, 2017;Thijs et al, 2014;Whang et al, 2014;Xiao et al, 2017). The other genera isolated have been registered in the literature as endophytic bacteria and plant growth promotors (Chen et al, 2001;Costa et al, 2016;Flores-Félix et al, 2014;Guglielmetti et al, 2013;Guimarães et al, 2012;Jaramillo et al, 2013;Mendis et al, 2018;Souza et al, 2015;Wang et al, 2017;Zhang et al, 2016;Zhao et al, 2017). Although the symbiotic relationships of these communities with siratro may be different from those with native Leguminosae species from each phytophysiognomy (Ribeiro et al, 2017;Santos et al, 2017), even rhizobia can act as PGPR by means of various processes, contributing to the sustainability of the ecosystems (Costa et al, 2016;Marra et al, 2012;Oliveira-Longatti et al, 2014).…”

“…It is widely reported that the nodules of legumes hold rhizobia together with other endophytic bacteria (Castro et al, 2017;Lima et al, 2009;Velázquez et al, 2017) whose role in symbiosis of legumes is little known. However, they may have positive effects since many of these endophytes had mechanisms for plant growth promotion (Armanhi et al, 2018;Costa et al, 2016;Rangel et al, 2016). It thus becomes necessary to study the application of these organisms in coinoculation studies on plants for revegetation in areas after mining activities.…”

“…Among these processes, we emphasize biological nitrogen fixation (BNF), carried out by symbiotic and associative diazotrophic bacteria, which is extremely important for the ecosystems by making nitrogen available in a form that can be assimilated by plants, which promotes greater plant development. Nevertheless, promotion of plant growth can be achieved through other processes, such as phytohormone production (Costa et al, 2016), phosphate solubilization (Angus et al, 2013;Costa et al, 2016), siderophore production (Wdowiak-Wróbel et al, 2017), and adaptation to stresses, such as tolerance to metals (Rangel et al, 2016), in leguminous and non-leguminous plants (Velázquez et al, 2017).…”

GROWTH RESPONSE OF Bauhinia Variegata L. TO INOCULATION AND ORGANIC FERTILIZATION

“…Literature reports that B. variegata is not capable of nodulation (Sprent, 2009), in agreement with the results in the present work. It was also verified that, independently form nodulation, there was a positive effect from inoculation over seedling height, dry mass of the aerial portion and roots, total dry mass, IQD and foliar contents of N and C. These effects may be attributed, probably not only to the capacity for biological fixation of N 2 , but also to the production of phytohormones (such as auxins, cytokinins and gibberellins) and solubilization of phosphates and exopolisaccharides by diazotrophic bacteria (Gumiere et al, 2014;Costa et al, 2016;Silva et al, 2016;Porto et al, 2016). As registered for strains of the genus Bradyrhizobium, which increased the production of Inga edulis (Porto et al, 2017), many arboreal species are responsive to inoculation, as also the normative from the Ministry of Agriculture, Livestock and Supply (Brasil, 2011) states, for approximately 23 arboreal legume species which have authorization to be inoculated in the seedling stage.…”

“…Basic research work of selection or recommendation of inoculants evidences that inoculation stimulates vegetal growth of various species. Works with cowpea showed results with various strains of symbiotic diazotrophic bacteria, established or native, producing hormones, solubilizing nutrients and increasing the biological fixation of nitrogen and productivity (Guimarães et al, 2012;Costa et al, 2016).…”