Plant growth-promoting capabilities of microorganisms and PCR amplification of nitrogen fixing (nif) gene in bacteria isolated from cassava plant rhizospheric soil from Ota, Ogun State, Nigeria

2025-04-14T05:39:28+00:00

The application of potent bacteria and fungi as bio-fertilizer can improve the soil nitrogen status leading
to enhanced soil well-being and agricultural production. Bacteria and fungi were isolated from soil
samples collected around 20 randomly selected cassava plants obtained from Bells University farm,
Ota. The isolates were screened for phosphate solubilization activity, indole acetic acid (IAA) production
and heavy metal tolerance using standard methods. Isolates were identified based on morphological
and sequencing of the amplified 16S rRNA and ITS genes for bacteria and fungi respectively. PCR
amplification of the nif gene was done using two primers. Results of the molecular identification showed
that the bacterial and fungal isolates were Pseudomonas resinovorans NOU6 (PP506413), Klebsiella
variicola NOU5 (PP506412), Kosakonia radicincitans NOU1 (PP493938) and Aspergillus assiutensis
NOU2 (PP493939), Aspergillus brunneoviolaceus NOU3 (PP493940) and Aspergillus tubingensis
NOU4 (PP493941) respectively. Indole acetic acid produced by bacterial and fungal isolates ranged
from 121-147 µg/ml and 14-33 µg/ml respectively. The three fungal isolates solubilized phosphate with
solubilization index (SI) ranging from 4.25 – 6.25. Results of the heavy metal tolerance test showed
that all bacteria isolates were sensitive to mercury while they showed tolerance to tin, cobalt, chromium
and iron though at varying degrees. Only Kosakonia radicincitans strain NOU1 (C5) habours the nif
gene that codes for nitrogenase enzyme. This research offers insights into the possible use of these
microorganisms as bio-fertilizers for crop improvement and also underscores the importance of using
molecular techniques to target bacteria strains that possess the potentials to fix atmospheric nitrogen.

Assessment of the impact of agricultural by-products on the dynamics of phytoplankton functional groups on a rice-fish farm in Bonoufla, Côte d'Ivoire

2025-04-19T16:06:40+00:00

The objective of this study was to determine the influence of agricultural by-products on the dynamics of phytoplankton functional groups’ abundance on a rice-fish farm. To this end, experiments were conducted in rice-fish ponds by introducing three categories of agricultural by-products: maize bran (RSM), rice bran (RSR), mixed agricultural by-products (RPC) and a control with no exogenous feed (RC). Data were collected monthly between May 2019 and November 2020 during the Pre-Grow-out and Grow-out phases of Oreochromis niloticus. Phytoplankton were sampled by water filtration using a 20 µm mesh plankton net. Algal cells were identified and counted. The Reynolds Functional Groups (RFG) classification was used to form the Phytoplankton assemblages with the dominant microalgae. Physicochemical parameters likely to influence algal proliferation were measured using a HQ40D multi-parameter and nutrient salts were determined using spectrometric methods. It was found that the phytoplankton flora of the rice-fish ponds was composed of 235 algal taxa, with a higher diversity of Chlorophyta and Euglenophyta. The specific richness of phytoplankton was virtually identical from one feeding treatment to the next. The phytoplankton in these ponds were grouped into 08 functional groups. The group J, represented by species of the genus Coelastrum, Lacunastrum, Desmodesmus and Scenedesmus, and group W2, represented by species of the genus Trachelomonas and Euglena, were the most abundant in all rice-ponds and in all months. The relative density of these functional groups increased monthly and significantly during each rearing phase with the RPC treatment compared with the other treatments. The proliferation of taxa in these functional groups was positively correlated with the concentration of nutrient salts, pH and dissolved oxygen content of the water in the rice-fish ponds. These results show that the J and W2 phytoplankton assemblages are effective indicators for monitoring organic pollution of rice-fish pond water.

Bio-Research

Plant growth-promoting capabilities of microorganisms and PCR amplification of nitrogen fixing (nif) gene in bacteria isolated from cassava plant rhizospheric soil from Ota, Ogun State, Nigeria

Assessment of the impact of agricultural by-products on the dynamics of phytoplankton functional groups on a rice-fish farm in Bonoufla, Côte d'Ivoire