Diversity of arbuscular mycorrhizal fungi in the rhizosphere of Plantago coronopus in Northwestern Algerian coast

Mycorrhizal fungi play a major role in the functioning of ecosystems. However, their identification has remained a challenge for scientific research. This study presents the first identification report of species of arbuscular mycorrhizal fungi in the rhizosphere of the halophyte Plantago coronopus L. in Algeria. Samples of rhizospheric soil were collected in spring 2018 at three sites in the Bomo-plage dunes west of Oran, Algeria. The spores were isolated by wet sieving, morphologically identified, and quantified. The mean spore density was 107.94 spores 100 g-1 dry soil, which is high compared to other dune ecosystems. Endomycorrhizal spore morphotypes were involved in the following Genus: Glomus, Septoglomus, Rhizophagus, Diversispora, Funneliformis, Dentiscutata, Claroideoglomus, Scutellospora, and Entrophospora, to the following Family: Glomeraceae, Gigasporaceae, Diversisporaceae, Claroideoglomeraceae, and Acaulosporaceae. The Glomeraceae was the most dominant identified family. The identification of indigenous arbuscular mycorrhizal fungi has been shown to be essential for future programs to restore disturbed dune ecosystems.

Pinibacter aurantiacus gen. nov., sp. nov., isolated from rhizospheric soil of a pine tree

A Gram-stain-negative, aerobic and rod-shaped novel bacterial strain, designated MAH-26T, was isolated from rhizospheric soil of a pine tree. The colonies were orange coloured, smooth, spherical and 0.7–1.8 mm in diameter when grown on Reasoner's 2A (R2A) agar for 2 days. Strain MAH-26T was able to grow at 10–40 °C, at pH 6.0–9.0 and with 0–1.0 % NaCl. Cell growth occurred on nutrient agar, R2A agar, tryptone soya agar and Luria–Bertani agar. The strain gave positive results in oxidase and catalase tests. Strain MAH-26T was closely related to Flavihumibacter sediminis CJ663T and Parasegetibacter terrae SGM2-10T with a low 16S rRNA gene sequence similarity (92.8 and 92.9 %, respectively) and phylogenetic analysis indicated that the strain formed a distinct phylogenetic lineage from the members of the closely related genera of the family Chitinophagaceae . Strain MAH-26T has a draft genome size of 6 857 405 bp, annotated with 5173 protein-coding genes, 50 tRNA and two rRNA genes. The genomic DNA G+C content was 41.5 mol%. The predominant isoprenoid quinone was menaquinone 7. The major fatty acids were identified as iso-C15:0, iso-C15:1 G and iso-C17:0 3OH. On the basis of phylogenetic inference and phenotypic, chemotaxonomic and molecular properties, strain MAH-26T represents a novel species of a novel genus of the family Chitinophagaceae , for which the name Pinibacter aurantiacus gen. nov., sp. nov. is proposed. The type strain of Pinibacter aurantiacus is MAH-26T (=KACC 19749T=CGMCC 1.13701T).

Biostimulatory Potential of Microorganisms from Rosemary (Rosmarinus officinalis L.) Rhizospheric Soil

Summary The objective of the present paper was to isolate microorganisms (Pseudomonas sp., Bacillus sp. and Azotobacter sp.) from the rhizospheric soil of rosemary (Rosmarinus officinalis L.) and investigate their biostimulatory (plant growth-promoting – PGP) and biocontrol potential. The bacteria isolated from the rhizosphere of rosemary included 15 bacteria of the genus Pseudomonas, 20 of the genus Bacillus, and 11 of the genus Azotobacter. Based on the morphological characteristics of colonies and cells, representative isolates of each genus were chosen (marked as Pseudomonas sp. P42, P43, P44; for Bacillus isolates B83, B84, B85, B92, B93; and for Azotobacter isolates A15 and A16) for different physiological and biochemical examination. The study included in vitro screening of the bacterial isolates for their PGP and biocontrol properties. Pseudomonas isolates showed the ability to live at low temperature (10ºC) and high pH (9), and to use different sources of carbon. All Pseudomonas isolates produced lipase, siderophore, hydrogen cyanide, and utilized organic and inorganic phosphorus, while only isolate P42 produced amylase, pectinase and cellulase. Only Bacillus isolates could grow at 45 ºC (all Bacillus isolates), pH 5 (isolates B83), and on a medium containing NaCl 5 and 7% (all isolates). Isolates denoted as B83 and B93 produced lipase, amylase, and pectinase. All isolates had the ability to solubilize phosphate, produce siderophores (except B85) and hydrogen cyanide, while only two isolates (B84 and B85) produced IAA. Azotobacter isolates had the optimal growth at 37ºC and minimal growth on a medium with pH 6 and 9. All Azotobacter isolates used all carbohydrates as a source of carbon and produced lipase, amylase, and hydrogen cyanide. The best result in suppressing the growth of pathogenic fungi Fusarium oxysporum was achieved by using isolate B92. Application of isolate B83 led to the greatest growth suppression of Sclerotinium sclerotiorum.

Isolation of Novel Vincristine and Vinblastine Producing Streptomyces Species from Catharanthus Roseus Rhizospheric Soil

Microorganisms could be used as efficient tools to protect high value therapeutic plants against overexploitation and climate change. This work aimed to isolate alkaloids producing endophytic and rhizospheric soil actinomycetes and fungi of Catharanthus roseus. From a total of eleven actinomycetes and eight fungi strains isolated by dilution and plate methods, six telluric actinomycetes were revealed to produce alkaloids according to the precipitation test of their extracts. Revelation by Thin Layer Chromatography method using vinblastine and vincristine standards on the basis of frontal reference values showed that the strain SC8 and the vinblastine, the strain SC7 and the vincristine displayed the same frontal references (0,89 and 0,88, respectively). Whole genome sequencing method showed that both strains belong to the genus Streptomyces with novel species.Moreover, metabolic pathways analysis from their genomes allowed to detect three enzymes involved in the biosynthesis of terpenoid backbone leading to that of terpenoid indole alkaloids.

Different Fertilizers Applied Alter Fungal Community Structure in Rhizospheric Soil of Cassava (Manihot esculenta Crantz) and Increase Crop Yield

Soil microbes play an important role in the ecosystem and have a relationship with plant growth, development, and production. There are only a few reports on the effects of planting patterns of cassava on the microbial community structure in the rhizospheric soil. Here, we investigated the effects of different fertilization on the microbial community structure in the cassava rhizospheric soil. SC205 cultivar was used in this study as the experimental material. Compound fertilizer (CF) and reduced fertilizer (RF) were applied to the soil prior to planting. Soil samples were collected before harvest, and fungi were analyzed using IonS5TMXL sequencing platform. Results showed that CF and RF treatments significantly increased cassava yield. Amplicon sequencing result indicated that the fungi richness in rhizospheric soil of cassava was increased after CF was applied, and the diversity was decreased. However, the fungal diversity and richness were decreased in rhizospheric soil after RF was applied. The most dominant fungal phylum was Ascomycota, which increased after fertilization. In addition, the abundance of beneficial fungi such as Chaetomium increased after fertilization, while that of pathogenic fungi such as Fusarium solani was decreased. The composition of the fungal community in rhizospheric soil with CF and RF applied was similar, but the richness and diversity of fungi were different. Canonical correspondence analysis (CCA) indicates there was a positive correlation between soil nutrition and fungal community structure. Overall, our results indicate that fertilization alters the fungal community structure of cassava rhizospheric soil, such that the abundance of potentially beneficial fungi increased, while that of potentially pathogenic fungi decreased, thereby significantly promoting plant growth and yield of cassava. Thus, during actual production, attention should be paid to maintain the stability of cassava rhizospheric soil micro-ecology.

Plant-microbe Interactions in Rhizospheric soil Treated with Different Quality Organic Residues

The objective of this research was to study plant-microbe interactions in rhizospheric soil treated with different quality organic residues in short-term incubation of the soil and subsequent planting of maize crop. The treatments combinations were, 1) untreated soil (control; CT), 2) groundnut stover (GN) with high nitrogen (N) but low lignin (L) and polyphenol (PP), 3) tamarind leaf and petiole litter (TM) with medium N, L and PP, 4) rice straw (RS) with low N, L and PP but high cellulose, 5) GN+TM, 6) GN+RS and 7) TM+RS. Single and mixed residue additions of GN and TM, both high and intermediate quality, resulted in higher soil microbial properties and nutrients than the application of RS as a low quality. Accordingly, the application of the former group increased microbial abundances (i.e., bacteria, archaea, and fungi), elevated the enzymes related to the decomposition of organic residue (i.e., invertase, protease, phenoloxidase and peroxidase activity), and enhanced soil nutrients and plant growth. The results indicated that the chemical compositions (N, L, and PP) of the organic residues amendment are key factors regulating soil microbial abundance and enzyme activity both in after incorporation and after planting. Moreover, bacterial and archaeal abundance, and microbial activities including soil respiration, invertase, protease, and peroxidase activity in the soil after planting higher than those in the soil before planting.

Response of contrasting bread wheat genotypes for heat and drought stress tolerance for rhizospheric soil properties

Aim: The study aimed at investigating differential response of contrasting bread wheat genotypes for heat and drought stress towards changes in chemical and microbial components of rhizospheric soil for developing climate resilient wheat varieties. Methodology: Rhizospheric soils were studied for changes in pH, electrical conductivity, cations, anions, micro-elements, major-elements, organic carbon and organic matter, and plant growth promoting rhizobacteria(PGPRs) abundance at booting and anthesis stages of growth in four contrasting genotypes during 2017-18 and 2018-19 crop seasons Results: The contrasting genotypes (HD2967 and WH730) for heat tolerance exhibited significant interaction between genotype and stage of growth for Na+, K+ and nitrogen, while genotypes (HUW468 and C306) for drought tolerance exhibited it for available nitrogen only. Significant difference for Ca2+, Mg2+, iron, manganese, nitrogen and potassium levels were recorded in drought stress related genotypes at two stages of growth. The heat tolerant genotype showed 2.54 and 10.67 folds enhancement in population of N2 fixing and spore forming bacteria at anthesis compared to sensitive genotypes, while drought tolerant genotype showed 1.51, 1.07 and 6.26 folds in P-solubilizing, N2 fixing and general bacterial abundance. Interpretation: Contrasting genotypes for heat and drought stresses responded differently for chemical properties and abundance of PGPRs in rhizospheric soils.

Different Soil Salinity Imparts Clear Alteration in Rhizospheric Bacterial Community Dynamics in Rice and Peanut.

The rhizospheric microbiome is capable of changing the physio-chemical properties of its own micro-environment and found to be indispensable in overall health of the host-plant. The interplay between the rhizospheric environment and the microbiota residing therein tune the physiology of the associated plant. In this study, we have determined how the soil properties and the host-plant remains as an important parameter for microbial community-dynamics in the rhizosphere of rice and peanut. In addition to check the physio-chemical parameters of the rhizospheric soil, we have also prepared the metagenomic DNA from each rhizospheric soil followed by high-throughput sequencing and sequence-analysis to predict the OTUs that represents the community structure. The alpha-diversity of the bacterial community in the RRN sample was highest, while the lowest was in PRS sample. Actinobacteria is the most predominant phylum in PRN, PRS and RRN whereas Acidobacteria in RRS. We found a clear shift in bacterial community over the rice and peanut rhizosphere and also over these host-rhizospheres from normal and high saline region. The rhizospheric bacterial community composition found to be affected by the close-by environmental factors. Thus, the rhizospheric bacterial community-structure is related to both the adjoining soil characters and the type of the hosts.