Phenotypic, stress tolerance, and plant growth promoting characteristics of rhizobial isolates of grass pea

Symbiotic N2 Fixation, Leaf Photosynthesis, and Abiotic Stress Tolerance of Native Rhizobia Isolated from Soybean Nodules at Da, Upper West Region, Ghana

The soybean is an important source of protein and is gaining popularity in Ghana due to a rising demand for its use in the poultry industry. However, the grain yield of soybeans is relatively low in the Upper West Region due to infertile soil and climate change. This study evaluated root nodulation and symbiotic effectiveness in 31 rhizobial isolates obtained from the nodules of soybeans planted at Da in the Upper West Region, Ghana, as well as measured photosynthetic activity of the soybean plants grown under glasshouse conditions. This study further assessed the tolerance of the rhizobial isolates to different levels of temperature, drought, salinity, and pH in the laboratory and also measured the ability of the isolates to produce indole-3-acetic acid. An infrared gas analyser and the 15N and 13C natural abundance techniques were used to assess the photosynthetic activity, N2 fixation, and water-use efficiency, respectively. The results showed that the test isolates that induced greater photosynthetic rates from higher stomatal conductance also stimulated increased water loss via leaf transpiration in soybean plants. Isolates TUTGMGH9 and TUTGMGH19 elicited much higher shoot δ13C in the soybean host plant and induced higher shoot biomass, C accumulation, percent relative symbiotic effectiveness, and N2 fixation relative to Bradyrhizobium strain WB74 and 5 mM of nitrate, which were used as positive controls. Although isolate TUTGMGH9 did not grow at 40 °C, it showed growth at 5% of PEG-6000, NaCl, and a low pH while also producing moderate IAA. However, for better utilisation of these rhizobial isolates as bioinoculants, their growth performance needs to be assessed under field conditions to ascertain their competitiveness and symbiotic efficacy.

Phenotypic and genotypic diversity of root nodule bacteria from wild Lathyrus and Vicia species in Gaziantep, Turkey

This study identified the phenotypic and genotypic characteristics of the bacteria that nodulate wild Lathyrus and Vicia species natural distribution in the Gaziantep province of Turkey. Principle component analysis of phenotypic features revealed that rhizobial isolates were highly resistant to stress factors such as high salt, pH and temperature. They were found to be highly sensitive to the concentrations (mg/mL) of the antibiotics neomycin 10, kanamycin, and tetracycline 5, as well as the heavy metals Ni 10, and Cu 10, and 5. As a result of REP-PCR analysis, it was determined that the rhizobial isolates were quite diverse, and 5 main groups and many subgroups being found. All of the isolates nodulating wild Vicia species were found to be related to Rhizobium sp., and these isolates were found to be in Clades II, III, IV, and V of the phylogenetic tree based on 16S rRNA. The isolates that nodulated wild Lathyrus species were in Clades I, II, IV, V, VI, VII, and VIII, and they were closely related to Rhizobium leguminasorum, Rhizobium sp., Phyllobacterium sp., Serratia sp., and Pseudomonas sp. According to the genetic analyses, the isolates could not be classified at the species level, the similarity ratio was low, they formed a distinct group that was supported by strong bootstrap values in the phylogenetic tree, and the differences discovered in the network analysis revealed the diversity among the isolates and gave important findings that these isolates may be new species.

Impact of Transgenic Maize Ruifeng125 on Diversity and Dynamics of Bacterial Community in Rhizosphere Soil

With the development of commercialized planting of genetically modified crops, their ecological security risks remain a key topic of public concern. Insect-resistant genetically modified maize, Ruifeng125, which expresses a fusion Bt protein (Cry1Ab-Cry2Aj), has obtained the application safety certificate issued by the Chinese government. To determine the effects of Ruifeng125 on the diversity and dynamics of bacterial communities, the accumulation and degradation pattern of the fusion Bt protein in the rhizosphere soil of transgenic maize were detected. Results showed that the contents of Bt protein varied significantly at different developmental stages, but after straw was returned to the field, over 97% of Bt proteins were degraded quickly at the early stages (≤10 d) and then they were degraded at a relatively slow rate. In addition, the variations in bacterial community diversity in the rhizosphere soil were detected by 16S ribosomal RNA (Rrna) high-throughput sequencing technology. A total of 44 phyla, 435 families, and 842 genera were obtained by 16S rRNA sequencing, among which Proteobacteria, Actinobacia, Acidobacter Acidobacterium, and Chloroflexi were the dominant taxa. At the same developmental stage, no significant differences in soil bacterial diversity were detected between Ruifeng125 and its non-transgenic control variety. Further analysis revealed that developmental stage, rather than the transgenic event, made the greatest contribution to the changes in soil microbial diversity. This research provides important information for evaluating the impacts of Bt crops on the soil microbiome and establishes a theoretical foundation for their environmental safety assessment.

Effect of glyphosate on the growth and survival of rhizobia isolated from root nodules of grass pea (Lathyrus sativus L.)

Grass pea (L. sativus L.) is a widely cultivated crop worldwide, forming a symbiotic relationship with nitrogen-fixing rhizobia. Glyphosate is commonly used by farmers for weed control during agricultural processes. However, the application of this chemical herbicide negatively impacts soil fertility by affecting the nitrogen-fixing rhizobia. This study aimed to assess the effects of glyphosate on rhizobia isolated from healthy and robust Grass pea plants. Specifically, Grass pea plants exhibiting vigorous growth and a healthy appearance were intentionally selected to isolate rhizobia from their root nodules. The isolated rhizobia were then characterized based on their morphological features, biochemical properties, and resistance to abiotic traits. Rhizobial isolates from grass peas exhibited Gram-negative, rod-shaped morphology, milky colony color, and variable colony sizes. Additionally, the majority displayed smooth colony surfaces on yeast extract mannitol agar medium. Based on morphological and biochemical characteristics, the isolates could be grouped under the genus Rhizobium. Optimum growth conditions for these isolates were observed at temperatures between 28 and 38 °C, pH levels ranging from 5 to 8, and salt (NaCl) concentrations of 0.5% and 1%. At a concentration of 20 mL L-1, glyphosate inhibited 5.52-47% of the Rhizobium population. The inhibition percentage increased to 17.1-53.38% at a concentration of 40 mL L-1. However, when exposed to a higher concentration (60 mL/L) of glyphosate, 87% of the isolates were inhibited. The number of colonies after glyphosate exposure was significantly dependent on concentration, and there were notable differences between treatments with varying glyphosate concentrations (p < 0.05). Glyphosate negatively impacted the survival of grass pea rhizobia, leading to a reduction in the Rhizobium population (CFU). However, the effect varied between Rhizobium isolated from grass pea root nodules.

Identification and growth-promoting effect of endophytic bacteria in potato

In agriculture, Bacillus species are efficient and ecologically tool for promote the growth of the plant.

Purpose: This study obtains the plant growth-promoting (PGP) ability of endophytic bacteria isolated from the potato tubers.

Methods: Using endophytic bacteria to promote potato growth, achieve the purpose of increasing production. In this experiment, the growth- promoting ability of the strain was verified by laboratory identification and field test validation.

Result: The isolates were identified as Bacillus species based on a 16S rRNA gene sequence and gyrB gene sequence analysis. DNA hybridization finally identified it as Bacillus velezensis. Among the PGP attributes, the strain K-9 was found to be positive for indole acetic acid (IAA) production, phosphate solubilization, siderophore production, and nitrogen fixation. The isolate was found negative for potassium solubilization. The quantitative estimation of IAA product to 9.09 μg/ml. The isolate also had the ability to produce lytic enzymes such as amylase and protease. The quantitative estimation of protease activity is 89.16 μg/ml. The inoculation strain K-9 improved bioaccumulation of roots and buds and yield in the potato compared to uninoculated control plants.

Conclusion: These findings give an insight into the ways to use PGP bacteria to increase potato production.

Obtaining Osmo-resistant Mutants in Nitrogen-Fixing Bacteria Isolated from Saline Soils

Annually, about, more than 7% of the Earth's land area becomes inappropriate for agriculture subsequently of salinization and desertification. Biofertilizers based on halophilic nitrogen-fixing bacteria can restore saline soils and stimulate plant growth, having a positive effect on germination, development of stems and roots, and fruiting. The aim of this work was to obtain osmo-resistant (Osm-r) nitrogen-fixing mutants isolated from saline soils of Armenia and selection of the best ones. To achieve this goal, we have obtained a collection of Osm-r strains based on soil nitrogen-fixing bacteria without the use of genetically modified technologies, which is an innovation in sphere of soil microbiology, and, especially, in nitrogen-fixing microorganisms. These mutants were obtained on the basis of Agrobacterium sp. Y-2 and Agrobacterium sp. M-1 nitrogen-fixing strains, both spontaneously and induced. Four strains with the higher nitrogen-fixing ability, which kept their vital activity in an environment with a high concentration of salts, were selected from collection of mutants. Selected strains in the future can become the basis for creating a new, effective, environmentally friendly biofertilizer for saline soils because they are plasmidless and have the highest priority for intensive use in agriculture.