Application of DNA barcodes and spatial analysis in conservation genetics and modeling of Iranian Salicornia genetic resources.

Iran is one of the origins of some Salicornia species. Nevertheless, comprehensive research has not been conducted on genetic potential, distribution, selection of populations, and the economic utilization of Salicornia in Iran. In the current study, Salicornia was collected based on the previous data available for 26 different geographical locations of provinces in Iran. We examined Salicornia plants' universality DNA barcodes, including rbcL, matK, trnH-psbA, and ITS, and their species identification abilities and identified six species groups. Subsequently, accurate modeling of distributed areas was provided with MAXENT and highlighted the valuable information on the diversity of specific geographical regions, conservation status of existing species, prioritization of conservation areas, and selection of Agro-Ecological areas. Together, this type of integrative study will provide useful information for managing and utilizing Salicornia genetic resources in Iran.

Mining the roots of various species of the halophyte Suaeda for halotolerant nitrogen-fixing endophytic bacteria with the potential for promoting plant growth.

Saline area may tend to be a productive land; however, many of salt-affected soils have nitrogen limitation and depend on plant-associated diazotrophs as their source of 'new' nitrogen. Herein, a total of 316 salinity tolerant nitrogen-fixing endophytic bacteria were isolated from roots of the halophyte Suaeda sp. sampled from 22 different areas of Iran to prepare the collection of nitrogen-fixing bacterial endophytes and evaluate the plant growth-promoting effect of effective isolates on growth of the halophyte Suaeda maritima. All of the identified nitrogen-fixing endophytes were classified to Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes phylum while we did not detect common nitrogen-fixing endophyte of glycophytes like Azospirillum. The genera Pseudomonas and Microbacterium were both encountered in high abundance in all samples, indicating that they might play an advanced role in the micro-ecosystem of the halophyte Suaeda. In addition, the results also showed that not only soil salinity can affect halophyte endophytic composition but also other factors such as geographical location, plant species, and other soil properties may be involved. Interestingly, only Zhihengliuella halotolerans and Brachybacterium sp. belonging to Actinobacteria could grow in semi-solid N-free (NFb) medium supplemented with 6% NaCl and highly enhanced growth of S. maritima in vitro. Overall, this study offers useful new resources for nitrogen-fixing endophytic bacteria which may be utilized to improve approaches for providing bio-fertilizer useful in saline-based agriculture.

Bio-based remediation of petroleum-contaminated saline soils: Challenges, the current state-of-the-art and future prospects.

Exploiting synergism between plants and microbes offers a potential means of remediating soils contaminated with petroleum hydrocarbons (PHCs). Salinity alters the physicochemical characteristics of soils and suppresses the growth of both plants and soil microbes, so the bioremediation of saline soils requires the use of plants and in microbes which can tolerate salinity. This review focuses on the management of PHC-contaminated saline soils, surveying what is currently known with respect to the potential of halophytes (plants adapted to saline environments) acting in concert with synergistic microbes to degrade PHCs. The priority is to identify optimal combinations of halophyte(s) and the bacteria present as endophytes and/or associated with the rhizosphere, and to determine what are the factors which most strongly affect their viability.

Mining alfalfa (Medicago sativa L.) nodules for salinity tolerant non-rhizobial bacteria to improve growth of alfalfa under salinity stress.

There are fewer reports on plant growth promoting (PGP) bacteria living in nodules as helper to tolerance to abiotic stress such as salinity and drought. The study was conducted to isolate rhizobial and non-rhizobial drought and salinity tolerant bacteria from the surface sterilized root nodules of alfalfa, grown in saline soils, and evaluate the effects of effective isolates on plant growth under salt stress. Based on drought and salinity tolerance of bacterial isolates and having multiple PGP traits, two non-rhizobial endophytic isolates and one rhizobial endophytic isolate were selected for further identification and characterization. Based on partial sequences of 16 S rRNA genes, non-rhizobial isolates and rhizobial isolate were closely related to Klebsiella sp., Kosakonia cowanii, and Sinorhizobium meliloti, respectively. None of the two non-rhizobial strains were able to form nodules on alfalfa roots under greenhouse and in vitro conditions. Co-inoculation of alfalfa plant with Klebsiella sp. A36, K. cowanii A37, and rhizobial strain S. meliloti ARh29 had a positive effect on plant growth indices under salinity stress. In addition, the single inoculation of non-rhizobial strains without rhizobial strain resulted in an increase in alfalfa growth indices compared to the plants non-inoculated and the ones inoculated with S. meliloti ARh29 alone under salinity stress, indicating that nodule non-rhizobial strains have PGP potentials and may be a promising way for improving effectiveness of Rhizobium bio-fertilizers in salt-affected soils.

Remediation of saline soils contaminated with crude oil using the halophyte Salicornia persica in conjunction with hydrocarbon-degrading bacteria.

The negative impact of salinity on plant growth and the survival of rhizosphere biota complicates the application of bioremediation to crude oil-contaminated saline soils. Here, a comparison was made between the remedial effect of treating the soil with Pseudomonas aeruginosa, a salinity tolerant hydrocarbon-degrading consortium in conjunction with either the halophyte Salicornia persica or the non-halophyte Festuca arundinacea. The effect of the various treatments on salinized soils was measured by assessing the extent of total petroleum hydrocarbon (TPH) degradation, the soil's dehydrogenase activity, the abundance of the bacteria and the level of phytotoxicity as measured by a bioassay. When a non-salinized soil was assessed after a treatment period of 120 days, the ranking for effectiveness with respect to TPH removal was F. arundinacea > P. aeruginosa > S. persica > no treatment control, while in the presence of salinity, the ranking changed to S. persica > P. aeruginosa > F. arundinacea > no treatment control. Combining the planting of S. persica or F. arundinacea with P. aeruginosa inoculation ("bioaugmentation") boosted the degradation of TPH up to 5-17%. Analyses of the residual oil contamination revealed that long chain alkanes (above C20) were particularly strongly degraded following the bioaugmentation treatments. The induced increase in dehydrogenase activity and the abundance of the bacteria (3.5 and 10 fold respectively) achieved in the bioaugmentation/S. persica treatment resulted in 46-76% reduction in soil phytotoxicity in a saline soil. The indication was that bioaugmentation of halophyte can help to mitigate the adverse effects on the effectiveness of bioremediation in a crude oil-contaminated saline soil.

Effective bioremediation of a petroleum-polluted saline soil by a surfactant-producing Pseudomonas aeruginosa consortium.

Bacteria able to produce biosurfactants can use petroleum-based hydrocarbons as a carbon source. Herein, four biosurfactant-producing Pseudomonas aeruginosa strains, isolated from oil-contaminated saline soil, were combined to form a bacterial consortium. The inoculation of the consortium to contaminated soil alleviated the adverse effects of salinity on biodegradation and increased the rate of degradation of petroleum hydrocarbon approximately 30% compared to the rate achieved in non-treated soil. In saline condition, treatment of polluted soil with the consortium led to a significant boost in the activity of dehydrogenase (approximately 2-fold). A lettuce seedling bioassay showed that, following the treatment, the soil's level of phytotoxicity was reduced up to 30% compared to non-treated soil. Treatment with an appropriate bacterial consortium can represent an effective means of reducing the adverse effects of salinity on the microbial degradation of petroleum and thus provides enhancement in the efficiency of microbial remediation of oil-contaminated saline soils.