**3.6 Microbes-assisted salt tolerance**

Microorganisms such as bacteria, mycorrhiza, and fungi are mostly used agents in mitigation of salt stress of *Brassica* inhabited in either the host plant or rhizosphere through promoting the growth of particular hosts [140; **Table 9**]. For instance, plantgrowth-promoting bacteria *Pseudomonas fluorescens* inoculation in *B. napus* proved to be an effective approach in mitigation of salt stress in *Brassica* crops, as the inoculated seedling under salt stress gave higher plant biomass, RWC, and Pro content for better osmoregulation during stressful conditions [142]. In saline soil, recovery of damaged *B. napus* was recorded by Latef et al. [146] as a consequence of *Azotobacter chroococcum* inoculation, whereas microbes not only improved plant morphological and physiological characteristics but also reduced Pro, MDA, and H2O2 contents to protect salt-induced cell damage. Additionally, the activities of antioxidant enzymes, namely SOD, POD, APX, were also augmented after inoculation conferring salt tolerance while reducing Na<sup>+</sup> level within the plants [146]. *Rhizobium* strains capable to produce ACC-deaminase improved nutrients (N, P and K) uptake of *B. napus* in salt-induced condition and thereby, growth parameters, such as plant height, DW, stem diameter, LN, and RWC, were also increased conforming salt tolerance to *B. napus* [143].


**Table 9.** *Microbes-assisted tolerance in Brassica under salt stress.* Inoculation of growth-promoting rhizobacterial strains *Pseudomonas* in regulation of salt mitigation activities of *B. juncea* has been confirmed by recording their positive role in increased GP, growth factors, ACC-deaminase activity, and aminolevulinic acid production even under high salt concentration [44]. Additionally, this microbe also takes part in auxin production, ETH reduction through ACC activity, and nutrient solubilization and so provides better establishment of *B. juncea* against extreme salt exposure [44].

The impaired growth of salt-induced *B. napus* can be ameliorated by applying mycorrhizae (*Glomus macrocarpium*), as inoculation of these microbes increases K+ /Na<sup>+</sup> in plant compared with salt-stressed plant alone, and so further abatement of salt damage was recorded in increased growth and yield parameters of *B. napus* with improved nutrient contents as well [148]. The amino acid and fatty acid profile also showed better performance in mycorrhizal inoculated plant under salt exposure in comparison with uninoculated stressed *B. napus* [148]. Moreover, proteins that are involved in cell function, leaf photosynthesis, redox potential, and amino acid metabolism are more prevalent in bacteria applied salt-stressed *B. napus* compared with salt-stressed seedling alone, and this is an important indication of salt tolerance mechanism induced by bacteria [142]. *B. napus* seed inoculation with *Arthrobacter globiformis* benefits higher GP with better seedling growth in high level of salt exposure, and this plant-microbe interaction also facilitates in higher phenolic compounds together with phenylalanine ammonia-lyase and SOD activities and more Pro accumulation as well to counteract salt-stressed damage in salt sensitive plants also [147].
