Bacterial endophytes employ various direct and indirect mechanisms for plant growth promotion under biotic stress upon colonization. To successfully establish endophytes as plant growth promoters, colonization and population density-dependent process, quorum sensing is essential. Therefore, the present study aimed at assessing the efficacy of foliar and basal application of two soybean plant growth-promoting bacterial endophytes having biocontrol activity against soybean anthracnose, namely Bacillus subtilis strain 5 (EB-1) and Bacillus amyloliquefaciens strain 14 (EB-2) in the soybean seedling. These two endophytes priliminarily screened for antibiotic resistance using a disc diffusion method to make the selective culture medium suitable for bacterial re-isolation from plant tissues. Bacterial endophytes were applied as foliar and basal inoculation on the soybean variety. Then, the bacterial population within the leaf tissues and rhizosphere soil was enumerated in the nutrient agar plate amended with antibiotics. Our study showed that the EB-1 and EB-2 showed significantly lower survival in the leaf tissues and the rhizospheric soils. However, the bacterium EB-1 and EB-2 survival rates were significantly higher in the leaf and soil tissue, respectively, compared with each other. Further, we identified the maximum survival period of these bacterial endophytes was 30 days in leaf tissue. Therefore, the present findings showed that endophytic bacterial suspension has to be applied at 30-day intervals. And we identified the maximum survival period of these bacterial endophytes in leaf tissue and soil and explained their role in providing biological control against diseases.

Bacillus subtilis (EB-1), Bacillus amyloliquefaciens (EB-2), colonization, antibiotic susceptibility, Anthracnose, and survival

We concluded that both the soybean bacterial endophytes applied through foliar and basal inoculation near the stem showed a significant decrease in the bacterial population. However, soybean bacterial endophytes could survive for up to 30 days in the leaf tissues. Therefore, we need to spray the bacterial suspension every 30 days to see the positive effect on plant growth and the inhibitory action against soybean anthracnose. Furthermore, other methods of bacterial delivery, such as seed treatments, should be tested for the survival and efficacy of the endophytes.

Sapna Jaiswal, Jayant Bhatt, Laxman Singh Rajput, Hemant Singh Maheshwari, Vibha Pandey, Mahaveer Prasad Sharma, Vennampally Nataraj and Sanjeev Kumar (2023). Soybean Bacterial Endophytes Bacillus subtilis (EB-1) and Bacillus amyloliquefaciens (EB-2) against Anthracnose survival in Leaf and Soil. Biological Forum – An International Journal, 15(12): 20-24.