Piriformospora indica is a root-interacting mutualistic fungus capable of enhancing plant growth, increasing plant resistance to a wide variety of pathogens, and improving plant stress tolerance under extreme environmental conditions. Understanding the molecular mechanisms by which P. indica can improve plant tolerance to stresses will pave the way to identifying the major mechanisms underlying plant adaptability to environmental stresses. We conducted greenhouse experiments at three different salt levels (0, 100 and 300 mM NaCl) on barley (Hordeum vulgare L.) cultivar “Pallas” inoculated with P. indica. Based on the analysis of variance, P. indica had a significant impact on the barley growth and shoot biomass under normal and salt stress conditions. P. indica modulated ion accumulation in colonized plants by increasing the foliar potassium (K⁺)/sodium (Na⁺) ratio, as it is considered a reliable indicator of salt stress tolerance. P. indica induced calcium (Ca²⁺) accumulation and likely influenced the stress signal transduction. Subsequently, proteomic analysis of the barley leaf sheath using two-dimensional electrophoresis resulted in detection of 968 protein spots. Of these detected spots, the abundance of 72 protein spots changed significantly in response to salt treatment and P. indica-root colonization. Mass spectrometry analysis of responsive proteins led to the identification of 51 proteins. These proteins belonged to different functional categories including photosynthesis, cell antioxidant defense, protein translation and degradation, energy production, signal transduction and cell wall arrangement. Our results showed that P. indica induced a systemic response to salt stress by altering the physiological and proteome responses of the plant host.

Aims The present study aimed at gaining an insight into the abundance and genetic diversity of culturable N‐fixing epiphyte bacteria on the phyllosphere of maize in arid and semi‐arid regions of Iran. Methods and Results Leaf samples of the maize variety, ‘single cross 704’ (Zea mays L.) were collected from different locations in Iran. The community of culturable N‐fixing epiphyte bacteria present was examined by 16S rRNA sequencing, BOXAIR‐polymerase chain reaction (PCR) and restricted fragment length polymorphisms analysis of 16S rRNA gene (16S‐RFLP). Approximately, 31·82% of the 242 isolates were identified as N‐fixers by cultivation of bacteria in Rennie medium and detection of their nifH gene. The N‐fixers were affiliated with four bacterial phyla: Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. 16S rRNA sequencing detected 16 genera and 24 different species in the identified phyla. The most dominant genus was Bacillus and the species identified were B. pumilus, B. amyloliquefaciens, B. subtilis, B. paralicheniformis, B. licheniformis, B. niabensis and B. megaterium. In total, 22 RFLP groups were present among the isolates originally identified as N‐fixing bacteria. BOXAIR‐PCR showed that there was a low similarity level among the N‐fixing bacteria isolates, and genetic differentiation of individual strains was relatively great. Conclusions Our findings suggest that nitrogen‐fixing epiphyte bacteria on the phyllosphere of maize may provide significant nitrogen input into arid and semi‐arid ecosystem. Significance and Impact of the Study This research implies that phyllosphere epiphyte diazotrophs have much to offer in sustainable agriculture and can be an alternative to chemical N‐fertilizers for providing nitrogen to crops arid and semi‐arid regions.