Assessment of two carrier materials for phosphate solubilizing biofertilizers and their effect on growth of wheat (Triticum aestivum L.).

Biofertilizers are usually carrier-based inoculants containing beneficial microorganisms. Incorporation of microorganisms in carrier material enables easy-handling, long-term storage and high effectiveness of biofertilizers. Objective of the present study was to assess enriched biogas sludge and soil as biofertilizer carriers on growth and yield of wheat. Six phosphate solubilizing strains were used in this study. Three phosphate solubilizing strains, 77-NS2 (Bacillus endophyticus), 77-CS-S1 (Bacillus sphaericus) and 77-NS5 (Enterobacter aerogenes) were isolated from the rhizosphere of sugarcane, two strains, PSB5 (Bacillus safensis) and PSB12 (Bacillus megaterium) from the rhizosphere of wheat and one halophilic phosphate solubilizing strain AT2RP3 (Virgibacillus sp.) from the rhizosphere of Atriplex amnicola, were used as bioinoculants. Phosphate solubilization ability of these strains was checked in vitro in Pikovskaya medium, containing rock phosphate (RP) as insoluble P source, individually supplemented with three different carbon sources, i.e., glucose, sucrose and maltose. Maximum phosphate solubilization; 305.6μg/ml, 217.2μg/ml and 148.1μg/ml was observed in Bacillus strain PSB12 in Pikovskaya medium containing sucrose, maltose and glucose respectively. A field experiment and pot experiments in climate control room were conducted to study the effects of biogas sludge and enriched soil based phosphorous biofertilizers on growth of wheat. Bacillus strain PSB12 significantly increased root and shoot dry weights and lengths using biogas sludge as carrier material in climate control room experiments. While in field conditions, significant increase in root and shoot dry weights, lengths and seed weights was seen by PSB12 and PSB5 (Bacillus) and Enterobacter strain 77-NS5 using biogas sludge as carrier. PSB12 also significantly increased both root and shoot dry weights and lengths in field conditions when used as enriched soil based inoculum. These results indicated that bacterial isolates having plant beneficial traits such as P solubilization are more promising candidates as biofertilizer when used with carrier materials.

Mukhtar S ，Shahid I ，Mehnaz S ，Malik KA ... -  《-》

Phylogenetic analysis of halophyte-associated rhizobacteria and effect of halotolerant and halophilic phosphate-solubilizing biofertilizers on maize growth under salinity stress conditions.

The main objective of the present work was to evaluate plant growth-promoting abilities of bacterial strains from the rhizosphere of halophytes and their effect on maize growth under salinity stress. Halophilic bacteria were identified using 16S rRNA sequence analysis and their plant growth-promoting abilities were characterized. Phylogenetic analysis showed that bacterial strains belonging to Bacillus, Halobacillus and Pseudomonas were dominant in the rhizosphere of halophytes. More than 93% strains showed P-solubilization activity and IAA production. About 54% strains were able to produce ACC deaminase, 29% strains showed positive results for nitrogen fixation, 41 and 21% strains showed siderophores and HCN production ability respectively. More than 90% strains showed antifungal activity against more than two fungal pathogens and production of different hydrolytic enzymes. To study the plant growth-promoting effect on maize, five bacterial strains Bacillus safensis HL1HP11 and Bacillus pumilus HL3RS14, Kocuria rosea HL1RP8, Enterobacter aerogenes AT1HP4 and Aeromonas veronii AT1RP10 were used as inoculants; in the form of seed coat and enriched soil-based phosphate biofertilizers. All bacterial strains positively affected the maize growth as compared to non-inoculated control + NaCl plants. Plants inoculated with Bacillus HL3RS14-based soil biofertilizers showed maximum increase in dry weights of root (48-124%) and shoot (52-131%) as compared to control + NaCl (soil + rock phosphate, no inoculum). PGPR inoculations under salinity stress conditions showed high concentrations of proline, glycine betaine and malondialdehyde. These results indicated that under saline soil conditions, halophilic PGPR strains combined with carrier materials are promising candidates as biofertilizers.

Mukhtar S ，Zareen M ，Khaliq Z ，Mehnaz S ，Malik KA ... -  《-》

Integrated use of phosphate-solubilizing Bacillus subtilis strain IA6 and zinc-solubilizing Bacillus sp. strain IA16: a promising approach for improving cotton growth.

Ahmad I ，Ahmad M ，Hussain A ，Jamil M ... -  《-》

Phosphate-solubilizing bacteria and silicon synergistically augment phosphorus (P) uptake by wheat (Triticum aestivum L.) plant fertilized with soluble or insoluble P source.

Phosphorus (P) deficiency is one of the major problems in agricultural soils for crop production around the world. Use of silicon (Si) and phosphate-solubilizing bacteria (PSB) is known as one of the most effective and economical ways for increasing P availability and improving P use efficiency under low P conditions. However, little is known about the alleviative role of Si and PSB together in mitigating P-deficiency stress and in improving P use efficiency in Triticum aestivum L. (wheat), as one of the most important crop plants worldwide. Consequently, aim of the research was to study the combined and single effects of Si (0, 150, 300, and 600 mg kg-1 added as silicic acid) and PSB (B0, Bacillus simplex UT1, and Pseudomonas sp. FA1) on P uptake by wheat plant fertilized with soluble or insoluble P (Esfordi rock phosphate, RP) in a completely randomized design with factorial arrangement through a perlite potted experiment. In addition, the effects of various treatments on wheat shoot and root dry weight, activity of catalase, superoxide dismutase, and peroxidase enzymes, and the uptake of Si and potassium (K) by this plant were also investigated. Both shoot and root biomass of wheat plants were markedly reduced when grown in RP-fertilized medium compared with those grown in soluble P-fertilized medium. The PSB strains and Si levels independently improved all the aforementioned parameters. Application of Si to wheat plants grown in soluble P or insoluble P medium markedly enhanced P use efficiency. According to the results of this study, Si not only increased the uptake of P from sparingly soluble-P source (RP), but also enhanced uptake of P from water-soluble P source. Both Pseudomonas sp. FA1 and B. simplex UT1 showed a considerable role in improvement of root and shoot biomass and uptake of P (and K and Si) under both soluble and insoluble P fertilization conditions with Pseudomonas sp. FA1 being more effective than B. simplex UT1. However, the combined application of the PSB with Si resulted in the greatest enhancement in wheat plant P uptake and other measured parameters. Addition of 600 mg Si kg-1 and Pseudomonas sp. FA1 significantly increased the P shoot concentration of wheat plant fertilized with RP to an adequate level (>0.3%) in the range of P-fertilized plants. Therefore, in addition to PSB application, Si should be considered as soil amendment in agricultural soils deficient in plant available Si as a means of sustainable agriculture with respect to possible savings of scarce P resources (P-fertilizers). The information on the availability of P following PSB and Si addition to plant growth medium may help in better management of P fertilization.

Rezakhani L ，Motesharezadeh B ，Tehrani MM ，Etesami H ，Mirseyed Hosseini H ... -  《-》

Role of Inorganic Phosphate Solubilizing Bacilli Isolated from Moroccan Phosphate Rock Mine and Rhizosphere Soils in Wheat (Triticum aestivum L) Phosphorus Uptake.

Azaroual SE ，Hazzoumi Z ，Mernissi NE ，Aasfar A ，Meftah Kadmiri I ，Bouizgarne B ... -  《-》