Isolation and Characterization of Halotolerant Plant Growth Promoting Rhizobacteria From Durum Wheat (Triticum turgidum subsp. durum) Cultivated in Saline Areas of the Dead Sea Region

Abstract

Plant growth promoting rhizobacteria (PGPR) are beneficial microorganisms that can be utilized to improve plant responses against biotic and abiotic stresses. In this study, 74 halotolerant bacterial isolates were isolated from rhizosphere and endorhizosphere of durum wheat ( Triticum turgidum subsp. durum ) plants cultivated in saline environments in the Ghor region near the east of the Dead Sea. 16S rDNA partial sequences and phylogenetic analysis of 62 isolates showed clear clustering of the isolates into three phyla: Firmicutes (61.3%), Proteobacteria (29.0%), and Actinobacteria (9.7%). At the genus level, the majority of them were grouped within the Bacillus, Oceanobacillus , and Halomonas genera. The isolates, which possessed plant growth promoting traits including nitrogen fixation, ACC deaminase activity, auxin production, inorganic phosphate solubilization and siderophore production, were selected. The effect of the inoculation of selected PGPR strains on growth of salt sensitive and salt tolerant durum wheat genotypes under high salt stress conditions was evaluated. Six halotolerant PGPR strains were able to improve survival in inoculated plants under high salinity stress conditions as reflected in higher germination percentages and seedling root growth when compared with non-inoculated plants. Furthermore, three halotolerant PGPR strains were able to improve durum wheat tolerance to water deficit stress. In addition, antagonistic effect in four halotolerant PGPR strains against an aggressive pathogenic isolate of Fusarium culmorum that causes crown rot disease was observed in a dual culture assay. In conclusion, the halotolerant PGPR strains described in this study might have great potential to improve durum wheat productivity under different stress conditions.

Halotolerant rhizobacteria Pseudomonas pseudoalcaligenes and Bacillus subtilis mediate systemic tolerance in hydroponically grown soybean (Glycine max L.) against salinity stress

“…One of the prime responses of salt stress is that it slows down the efficiency of water uptake by the plants and disturbs the osmotic balance leading to apoptosis. In this situation, the compatible osmolyte proline activated and tried to mitigate the effects of salt [2]. Our results showed that the plants inoculated with the P. pseudoalcaligenes recorded significantly higher proline level and reduced malondialdehyde under salt stressed conditions in comparison to un-inoculated salt affected plants.…”

“…Plant-growth-promoting bacteria (PGPB) are capable of enhancing plant growth by colonizing plant roots that can benefit the plant [1]. Among those, the halotolerant PGPB can withstand higher concentration of salt [2]. Halotolerant PGPB can promote plant growth and indirectly develop tolerance against stress by altering the selectivity of Na + , K + , and Ca 2+ to sustain a higher K + /Na + ratio, regulating the various antioxidant enzymes levels in the cells.…”

“…Salinity is one of the foremost abiotic stresses that have severe impact on crop cultivation through limiting the environmental resources especially the physicochemical characteristics of soil [7]. Major contributors for increased salinity stress include firstly, poor cultural practices such as inappropriate fertilizer application and water management; secondly, climate change such as high evaporation with low rainfall [2]. Generally, salinity has negative effects on almost all stages of plant life cycle [8].…”

“…Ability of halophytes to cope up with the salt stress is related to various developed mechanisms to reduce the negative effects of salt stress. They include ion pumps, abscisic acid (ABA), osmoprotectants and ROS scavenging mechanism [2]. In order to develop strategies to increases salt tolerance in plants, a thorough understanding of salt tolerant mechanism against salinity stress is essential.…”

“…The deleterious effects of salinity in soybean have been reduced by several conventional and non-conventional strategies such as seed priming, growth regulators, signalling molecules and salt tolerant varieties [12]. It has been proved from numerous studies that many bacterial strains belonging to different genera could efficiently reduce the deleterious effects of salinity stress [2].…”