Jadson Emanuel Lopes Antunes

Interrelationship of Bradyrhizobium sp. and plant growth-promoting bacteria in cowpea: Survival and symbiotic performance

The objective of this study was to evaluate the survival of cowpea during bacterial colonization and evaluate the interrelationship of the Bradyrhizobium sp. and plant growth-promoting bacteria (PGPB) as a potential method for optimizing symbiotic performance and cowpea development. Two experiments using the model legume cowpea cv. “IPA 206” were conducted. In the first experiment, cowpea seeds were disinfected, germinated and transferred to sterilized Gibson tubes containing a nitrogen-free nutritive solution. The experimental design was randomized blocks with 24 treatments [Bradyrhizobium sp. (BR 3267); 22 PGPB; absolute control (AC)] with three replicates. In the second experiment, seeds were disinfected, inoculated according to their specific treatment and grown in Leonard jars containing washed and autoclaved sand. The experimental design was randomized blocks with 24 treatments [BR 3267; 22 BR 3267 + PGPB; AC] with three replicates. Scanning electron microscopy demonstrated satisfactory colonization of the roots of inoculated plants. Additionally, synergism between BR 3267 and PGPB in cowpeas was observed, particularly in the BR 3267 + Paenibacillus graminis (MC 04.21) and BR 3267 + P. durus (C 04.50), which showed greater symbiotic performance and promotion of cowpea development.

Less abundant bacterial groups are more affected than the most abundant groups in composted tannery sludge-treated soil

The application of composted tannery sludge (CTS) has promoted shifts in soil chemical properties and, therefore, can affect the soil bacterial community. This study assessed the effect of the CTS on the soil bacterial community over time. The CTS was applied at five rates (0, 2.5, 5, 10 and 20 t/ha), and the bacterial community was evaluated for 180 days. The principal curve response (PRC) analysis showed that the most abundant phyla were not influenced by the CTS rates over time, while the analysis of the bacterial community showed that some of the less abundant phyla were influenced by the CTS rates. Similarly, the PRC analysis for the bacterial classes showed the significant effect of the CTS rates. The redundancy analyses for the bacterial phyla and classes showed the relationship between the significant chemical properties and the bacterial community of the soil after the CTS amendment over time. Therefore, there was a shift in the bacterial community over time with the application of the composted tannery sludge. Our study has shown that the less abundant bacterial groups were more influenced by the CTS than the most abundant bacterial groups and that these bacterial groups were driven by soil chemical properties, primarily chromium (Cr) and the soil pH.

Selection of plant growth-promoting bacteria in sweet sorghum ( Sorghum bicolor (L.) Moench) under the effects of salinity

Background Sorghum, a grassy non-halophyte, it is both drought and salinity tolerant, and is considered a promising crop for semiarid regions. During the last 20 years, its culture has expanded in Brazilian production by 780%, reaching 1,928,970 tons in 2009 [1]. Salinization of the soil and lack of rain are increasing constraints in semiarid regions. They predominate in northeastern Brazil. This has helped limit the production of plant biomass, which is the basis of agricultural activity. The advantages of sorghum in these conditions can be improved still further by using plant growth-promoting bacteria (PGPB) for the biological processes of nitrogen fixation, and hormone production, as well as others [2]. Endophytic bacteria can secrete up to one half of the nitrogen they fix, and plants may then assimilate the nitrogen efficiently [3]. Inoculation with Azotobacter chroococcum has been shown to attenuate stress in maize grown in saline soil [4]. In this study, we evaluated the action of PGPB on a “Wray” saccharine variety with low salinity tolerance.