Microbial Consortium-Induced Changes in Oxidative Stress Markers in Pea Plants Challenged with Sclerotinia sclerotiorum

The ability for rhizobacteria and fungus to act as bioprotectants via induced systemic resistance has been demonstrated, and considerable progress has been made in elucidating the mechanisms of plant–biocontrol agent–pathogen interactions. Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27, and Bacillus subtilis BHHU100 from rhizospheric soils were used singly and in consortium and assessed on the basis of their ability to provide disease protection by relating changes in ascorbic acid and hydrogen peroxide (H₂O₂) production, lipid peroxidation, and antioxidant enzymes in pea under the challenge of Sclerotinia sclerotiorum. Increased production of H₂O₂ 24 h after pathogen challenge was observed and was 254.4 and 231.7–287.7 % higher in the triple consortium and singly treated plants, respectively, when compared to untreated challenged control plants. A similar increase in ascorbic acid content and ascorbate peroxidase activity was observed 24 and 48 h after pathogen challenge, respectively, whereas increased activities of catalase, guaiacol peroxidase, and glutathione peroxidase were observed 72 h after pathogen challenge. Similarly, lipid peroxidation reached a maximum at 72 h of pathogen challenge and was 61.2 and 11.2–32.1 % less in the triple consortium and singly treated plants, respectively, when compared to untreated challenged control plants. These findings suggest that the interaction of microorganisms in the rhizosphere enhanced protection from oxidative stress generated by pathogen attack through induction of antioxidant enzymes and improved reactive oxygen species management.