The biocontrol efficacy endophytic bacteria against fungal plant pathogens Cercospora punicae and Ceratocystis fimbriata

Abstract With the constant raise in the world population, the demand for food supply has increased. Even though the use of agrochemicals helps in controlling pests and pathogens and increasing yield, it causes major environmental pollution. Hence, biocontrol which involves the use of living organisms or their metabolic by-products to control pests and pathogens, is important. Endophytes are a major biocontrol’s used and their association with other symbiotic bacteria helps in improving nutrient acquisition and resistance. In the present study the biocontrol efficacy of six endophytic bacteria (bacterial consortium) were assessed against two fungal pathogens (Cercospora punicae and Ceratocystis fimbriata). The seedlings were inoculated with bacterial consortium (Test). The untreated seedlings were labelled as Control. They were challenge inoculated with fungal pathogens and the plant growth parameters were recorded for 45 days. Percentage of infection, biological control efficacy, and disease incidence were calculated. The successful transmission of the endophytes was assessed through isolation of the endophytes from the soil and the seedlings and imaging the plant tissues using confocal microscope. The ability of endophytes to release certain bioactive compounds like chitinase, siderophores, indole acetic acid, hydrogen cyanide, and 2,4- Diacetyl phloroglucinol was also analysed. The seedlings in Test showed better growth and resistance against fungal pathogens when compared to Control. The biocontrol efficacy was 87.45 ± 2.55 and 88.47 ± 2.79% in Test respectively. Confocal imaging showed successful transmission of endophytes into the plant tissue. The endophytes were able to release bioactive compounds, thus increasing the plant’s ability to resist fungal pathogens and grow.