Induced Systemic Resistance-Mediated Defense Against Alternaria Blight Disease in Lentil by Pesticide Degrading Plant Growth-Promoting Rhizobacteria.

Enzymatic and antioxidative responses are key defense mechanisms in plants following pathogen invasion, collectively known as induced systemic resistance (ISR). Alternaria sp., a well-known soil-borne pathogen, causes blight diseases in various crops. This study investigates the defence response in lentil plants through the treatment-induced application of two multipotent pesticide degrading plant growth-promoting rhizobacteria (PGPR), Bacillus cereus and Bacillus safensis, to mitigate the destructive effects of Alternaria. Both bacterial strains were applied in different carrier-based bioformulations via soil drenching. We assessed the modulation of defense-related enzymes by various combinational treatments with the Alternaria pathogen. The in vitro production of antimicrobial compounds was analyzed using GC-MS to confirm their pathogen-suppressive capabilities. Field trials showed a positive correlation between treatments and improvements in yield and growth index (GI). The highest (180%) enzymatic induction of phenylalanine ammonia lyase (PAL) followed by catalase (CAT)(100%) and polyphenol oxidase (PPO) (54%), was observed in treatments with B. cereus alone or in combination with B. safensis, in presence of Alternaria, in respect to the control. In vitro analysis revealed the production of antimicrobial compounds, including benzoic acid derivatives, cyclotetrasiloxanes, hexacosane, chlorpyrifos, and phthalates, which may contribute to pathogen suppression. Our findings demonstrate that these biocontrol agents (BCAs) not only stimulate the plant's enzymatic defense system but also enhance growth, seed yield and produce several antimicrobial compounds in vitro. Thus, pesticide-tolerant PGPR, used in this study, exhibit both disease control and plant growth-promoting properties, offering promising applications in sustainable agriculture.