Journal of Soil Biology
Year:2019 | Volume:7 | Issue:2|Papers Count:9

Plant growth promoting rhizobacteria (PGPRs) are a group of bacteria that enhance plant growth through direct and indirect effects. Isolation of PGPRs from Sophora alopecuroides rhizosphere and assessment of their plant growth promoting traits was the main aim of this study. Fifty two bacterial isolates were isolated from Sophora alopecuroides rhizosphere and their phenotypic and morphological characteristics were studied. Phosphate solubilization and production of ammonia, indole acetic acid, protease, lipase and HCN were evaluated in vitro. Phosphate solubilizing ability was assayed using PVK and NBRIP media. The results showed that the number of isolates with phosphate solubilization ability was 44 and 18 in those two media, respectively. The range of indole acetic acid production in isolates was 0. 12 to 37 μ g ml-1. The percentage of isolates which were capable to produce ammonia, protease, lipase and HCN were 83%, 87%, 87% and 65%, respectively. According to the results, three isolates (named as 20, 37 and 48) which showed positivereaction in phosphate solubilization, production of ammonia and indole acetic acid production tests, were introduced as the strains having capacity for using as biofertilizers. Two isolates (named as 13 and 43) with strong positive reaction in the tests of protease, lipase and HCN production; were regarded as potential candidates for using as biocontrol agents. The partial sequence of 16S rRNA gene of selected isolates was determined and the derived sequences were compared against the GenBank database using NCBI, BLASTN. Based on morphological and biochemical characters and also 16S rDNA sequence, some of isolates were belonged to genera of Bacillus, Pseudomonas, Acinetobacter and Arthrobacter. The result of this study indicated that the proportion of PGPRs in rhizosphere of Sophora alopecuroides is high.

Cellulolytic bacteria with cellulase enzyme system play an important role in decomposing lignocellulose wastes and accelerating the composting process. For this purpose, a study was carried out on some native cellulolytic bacteria isolated from different sources in Soil and Water Research Institute. Twenty eight isolates were selected based on morphological characteristics and cellololytic test, in specific medium (B. H. M). Spot cultivation on B. H. M medium and observation of halo diameter as the cellulolytic characteristics of the isolates led to the separation of 12 isolates. The maximum and minimum diameter of a clear zone around the colony of MAL and HSE isolates were 31 and 8 millimeters respectively. Also the maximum and minimum proportion of clear zone diameter to colony were observed in TER and CPL isolates. The activity of endoglucanase, exoglucanase and betaglucosaidase among 12 isolates showed that the least amount of endoglucanase was belong to SAD (0. 17 U. ml-1) and the most one was NTL (2. 55 U. ml-1) isolates. The maximum activity of betaglucosidase in NTT isolate was 0. 31 U. ml-1 and the maximum exoglucanase enzyme activity was belong to HPN isolate (0. 35 U. ml-1)and minimum was belong to BSB isolate (0. 18 U. ml-1). Analysis of variance showed that the differences between the isolates with the highest and lowest triple cellulase activity was significant (especially endoglucanase (at one percent statistic level but was not significant between some isolates. There was a direct relation between cellulase activity and the enzyme compound. NTT isolate showed the highest activity of beta-glucosidase enzymes and it was the second and the third in terms of endoglucanase and exoglucanase production, respectively. It had the highest activity of three enzymes (3. 21 unit) and identified and registered as Bacillus methyltrophicus.

In order to evaluate the influence of different plant biomass on vermiculture and vermicomposting, a greenhouse experiment was conducted for 90 days in Shahid Chamran university of Ahvaz during 2017. Experimental design was factorial based of RCB with 3 replications. First factor was three plant biomass types (sesame, wheat and sugarcane) and second factor was initial earthworm weight (60-75 and 90 grams). Biological characteristics of earthworm and vermicompost’ s chemical characteristics were measured. The results showed that the highest mature earthworm weight (122. 79 g) and total earthworm weight (209. 57 g) were belonged to sesame biomass with 90 g of earthworm weight. This treatment also had a highest phosphorus rate (158. 5 mg/kg). The lowest mature earthworm weight (63. 15 gr) was belonged to sugarcane biomass with 60 g of earthworm weight. Also, applying sesame biomass with 60 g earthworm weight had a highest efficiency ratio (2. 8). In conclusion, we found that both plant biomass type and initial earthworm weight had different effect on earthworm biological characteristics. In other words, applying sesame plant biomass was suitable for increasing growth rate and maturity of earthworms. Also applying sugarcane plant biomass was suitable for increasing earthworm reproduction. In addition, for the optimum availability of nitrogen, phosphorus and potassium in the final vermicompost was appropriate to use sugarcane, sesame and wheat biomass, respectively.

Azospirillum bacteria are one of the most important plant growth promoting rhizobacteria which exist in the rhizosphere of many crop plants. In this research, some soil and plant roots were collected from wheat and maize rhizosphere of the fields in Isfahan and were cultured in the tubes containing Nitrogen Free Bromothymol (NFB) medium. In order to isolate Azospirillum strains, the grown bacteria pellicles were streaked on NFB and Rojo Congo (RC) specific and semi-specific media. The bacteria were isolated and purified using morphological characteristics on the medium. After gram staining, catalase, oxidase and oxidative-fermentative tests, the detection and identification of Azospirillum isolates was done by molecular tests using PCR test with Az16S-A and Azo494-F/Azo756-R specific primers and 16S rRNA gene sequencing. Plant growth promoting characteristics (PGP) of Azospirillum isolates were determined by investigating the presence of NifH and NifD genes of nitrogenase enzyme by PolF/PolR and FdB260/FdB261 specific primers respectively. The properties of phosphate solubilization and production of chitinase, HCN, siderophores and indole acetic acid of isolates were performed by using specific tests. The replication of 646, 263, 360, and 390 bp fragments by Az16S-A, Azo494-F/Azo756-R, PolF/PolR and FdB260/FdB261 primers respectively, confirmed the presence of Azospirilum bacteria and the presence of NifH and NifD genes. Specific tests also revealed the ability of indole acetic acid production, insoluble phosphate solubilizationwith average value of 15 and 18. 8 mg/l respectively and siderophore production in isolates. The results showed that some of the isolates possessed several PGP properties, while some of them had one or no characteristic. Finally, the sequencing of the 16S rRNA gene in some isolates determined and three species of A. brasilense, A. lipoferum and A. zeae identified in rhizosphere of wheat and maize plants.

In this study, 16 contaminated soil samples (with petroleum products) were collected from four different sites at Marun oil field of Ahwaz. Thirty three fungal isolates were isolated and purified using single-spore and hyphal-tip methods. 23 fungal isolates were selected for morphological and molecular identification. The mycelial biomass of the purified fungal isolates was produced into potato-dextrose-broth medium. DNA samples were extracted from freeze-dried mycelia and ITS and Glycerol-3-phosphate dehydrogenase (GPDH, only for Curvularia) regions were amplified using appropriate primers. Amplified products were purified using ethanol precipitation and gel extraction, and sequenced by Macrogen Company. The obtained sequences were edited and assembled and then used in BLASTn search and ML phylogenetic analysis. Fungal isolates were identified using morphological and molecular studies as follow: Acremonium sclerotigenum, Alternaria destruens, Aspergillus sp., Cladosporium puyae, Curvularia sp., Fusarium sp., Mucor circinelloides, Penicillium oxalicum, P. chrysogenum, Paramyrothecium terrestris, Rhizopus oryzae and the isolates of both Allophoma and Neodidymelliopsis genera from the family Didymellacae. Both the Cladosporium puyae and Paramyrothecium terrestris are new records in IRAN Mycobiota

Common myrtle (Myrtus communis L. ) spread in arid and semi-arid regions of Iran which it has many uses in different ways. In order to investigation of microbial inoculation influence on the physiological changes of M. communis seedlings under water deficit conditions a greenhouse experiment as a factorial in a completely randomized design with three replications was conducted. Water deficit consisted of 30% field capacity (FC) (severe stress), 60% FC (mild stress) and 100% FC (without stress), and microbial inoculations were including of Funneliformis mosseae, Rhizophagus intraradices, combination of these two fungal, Pseudomonas fluorescens, P. putida, combination of these two bacteria, and also control (without inoculation). According to the results, in each water regime the highest root colonization was observed in the combination of two fungal. This treatment promoted root colonization by 17. 8, 11. 3 and 7. 75 times in 30% and 60% and 100% of FC treatments respectively compared to the control. Microbial inoculation improved plant yield efficiency in water deficit conditions. In severe water deficit treatment, combined treatments of fungal or bacterial increased photosynthesis (47-48%), stomatal conductance (39-41%), transpiration (62-65%), mesophyll conductance (57-64%), water potential (20-21%), and relative water content (1. 4 times), and decreased intracellular CO2 concentration (28-31%) and electrolyte leakage (1. 4 times) compared to the control. It can be suggested that microbial inoculation can encourage drought resistance of M. communis seedlings to water deficit.

Using biofertilizers and weed control can be effective on improving of chickpea yield. In this study, a factorial experiment was conducted in a RCBD with three replications at Ferdowsi University of Mashhad. Experimental Factors included the application of biofertilizers in six levels (phosphate solubilizing bacteria (Bacillus +Pseudomonas), potassium solubilizing bacteria (Thiobacillus sp. ), pseudo-mycorrhizae (Piriformospora indica), Bacillus + Pseudomonas + Thiobacillus, Bacillus + Pseudomonas + Thiobacillus + Piriformospora, and control treatment) and weeds control at three levels (weed control with combination of pyridate and cletodim herbicides, two and three times weeding). Results showed that the distance of the first branch from the soil surface was not affected by biological fertilizers and weed control treatments although it was increased with application of biological fertilizers. The highest pod distance from the soil surface was observed in phosphate solubilizing bacteria + two weeding treatment. The maximum number of main branches per plant was obtained in phosphate solubilizing + two weeding treatment. The highest number of lateral branches per plant was observed in potassium solubilizing bacteria treatment + phosphate solubilizing bacteria + weed control using combination of pyridate and cletodim herbicides. Concomitant using of potassium solubilizing bacteria with phosphate solubilizing bacteria increased the number of pods per plant by 30% compared to the control treatment. There were no significant differences between chemical and weeding of weed control treatments in terms of number of pods per plant. Concomitant consumption of potassium + phosphate solubilizing bacteria and concomitant application of potassium + phosphate solubilizing bacteria along with endophytic fungi mycorrhiza produced the highest chichpea biomass and seed yield. The application of pyridate + cletodim herbicides reduced seed yield to 29 and 24 percent, respectively, compared with two and three times weeding. The highest concentration of shoot phosphorus was obtained in the treatment of endophytic fungi and chemical control of weeds and the highest concentration of potassium was obtained in the combination treatment of potassium and phosphate solubilizing bacteria and endophytic fungi. Generally, in this study biological fertilizers had a positive effect on yield and yield components of chickpea, although the application of combination of pyridate and cletodim herbicides had a negative effect on chickpea yield.

Phosphorus is one of the most important and essential elements for plant growth but it is not available for plants in many soils. Inoculation of paddy soils with phosphate solubilizing cyanobacteria is an efficient procedure for supplying phosphorus for rice plants. In this study, cyanobacteria isolated from Guilan paddy fields and purified. Cyanobacteria isolates identified by using morphological characteristics and molecular techniques. Their phosphate solubilization ability was evaluated and then superior strains for rice pot planting (Tarom Hashemi cultivar) was selected. A greenhouse experiment was conducted to evaluate the selected cyanobacteria isolates. The experiment carried out in a factorial completely randomized design with four levels of nitrogen (0, 0. 23, 0. 45 and 0. 46 g urea per pot) and seven strains of cyanobacteria and control without bacteria with three replications. The results showed that the isolates were classified into four phyla of Chroococcales, Oscillatoriales, Nostocales and Stigonematales. Anabaena sp. GGuCy-17 strain had the highest phosphate solubilizing potential (641 mg. L-1) compared to other strains, and the Cylendrospermum sp. GGuCy-25 (130 mg. L-1) was the second in this respect. The highest grain yield (15. 6 g. pot-1), the highest total nitrogen (14. 3 g. pot-1) and phosphorus uptake (2. 8 g. pot-1) were obtained in plants inoculated with Cylindrospermum sp. GGuCy-25. After further studies in different paddy field conditions, these efficient strains could be accounted for production of cyanobacterial biofertilizers to improve rice growth and yield.