Interaction between Piriformospora indica and Azotobacter chroococcum diminish the effect of salt stress in Artemisia annua L. by enhancing enzymatic and non-enzymatic antioxidants

Artemisia annua is a medicinal plant known for artemisinin, a potential anti-malarial drug. In this study, we investigated how the mutualistic and synergistic interaction between Piriformospora indica (Pi) and Azotobacter chroococcum (Az) ameliorates the damaging effects of salinity on A. annua L. Our findings revealed that dual treated plants had better plant height, dry weights of shoot and root under salt stress than the un-inoculated ones. During salt stress, microbial treated plants reduced the oxidative damage in plants by decreasing the concentrations of MDA [Pi (up to 44%), Az (up to 22%), Pi+Az (up to 61%)], and H2O2 [Pi (up to 45%), Az (up to 28%), Pi+Az up to 57%)]. It was unveiled that the enhancement in activities of enzymatic and non-enzymatic antioxidants is probably the main mechanism underlying salt tolerance in microbial treated plants. During salt stress, dual inoculation of Pi and Az resulted an enhanced activities of antioxidant enzyme (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and non-enzymatic antioxidants (total flavonoids, phenolics and carotenoids). Also, increase in artemisinin (56-64%) and proline (82-88%) content was recorded in co-inoculated plants (Pi+Az). These findings demonstrated the potentiality of Pi and Az dual symbiosis act as bio-ameliorator under saline conditions. This tripartite plant-microbial relationship could be a promising practice to alleviate the negative impact of salt stress on the productivity of medicinal plants.