The microbes present in the soil near crop plants’ roots can have powerful effects on the success of the plants, such as suppressing potential pathogens and nourishing plants for stronger growth. But what does a great microbial combination look like for our most beloved crops, and how big is that community? Khokhani Lab PhD student Pranaya Kaki recently led a study digging into the microbial secrets to success for corn, one of the United States’s most important crops, building on past research showing a successful consortium of seven bacteria (C7) as a successful biological control for corn seedling blight caused by Fusarium verticillioides. Biological control is a valuable alternative to excessive reliance on chemical fungicides, which prevent many common pathogens but pose environmental risks like soil contamination, decreased soil respiration, and disruption to soil enzyme activity, among others.
Kaki and collaborators approached this question aiming to evaluate biological control efficacy of bacterial consortia against four major corn pathogens: Pythium torulosum, Fusarium graminearum, Fusarium subglutinans, and Rhizoctonia solani. In order to expand on the success of past bacterial biocontrol using C7, Kaki investigated adding a nitrogen-fixing bacterium, Azotobacter vinelandii (S8), into the C7 mix to form “C8,” and also did testing and analysis on whether specific subcommunities of the C7 community were driving most of the benefits by testing with subcommunities dubbed SC1, SC2, and SC3.
To test the efficacy of these communities and subcommunities, Kaki et al. used both plate assays and growth-chamber trials with surface-sterilized corn seeds of the B73 genotype. She cultured the four fungal corn pathogens listed above, as well as the individual bacterial strains forming C7/C8, which were used to form mixed C7/C8 communities as well as subcommunities SC1, SC2, and SC3. The sterilized corn seeds were soaked in the inoculum of the different bacterial combinations before being planted in a potting mixture sprinkled with pathogen-infested sterile sorghum seeds. The corn, immersed in both the different combinations of bacterial consortia and fungal pathogens, was then grown and analyzed in indoor growth chambers, where height and root biomass were measured and noted. Bacterial strains plated in media were also plated, DNA extracted, amplified with PCR, and sequenced. For a complete description of methods, please read the full publication in Frontiers in Microbiology.
These results indicated that a strategic selection of bacterial strains is more important for biocontrol efficacy than building a broad community. Both S8 and C8 showed improved inhibition of P. torulosum than the original C7, bringing over 65% growth inhibition. S8 and C8 were less effective against Fusarium spp, with only 25-30% inhibition, and R. solani growth was not inhibited by any combination. Although S8 was effective by itself, that effect didn't hold once integrated into C7 community. Moreover, the temporal relative abundances suggested that S8 was outcompeted by the C7 community. This suggested that the corn root bacterial consortium is resilient to invasion. We selected our subcommunities by comparing the traits across plant phenotypes and in vitro effects. Bacterial subcommunities also made clear impacts on overall plant health, as well—plants that received combinations SC1 and SC2 showed restored and enhanced plant height and root biomass in the growth-chamber trials.
Based on these findings, it would be valuable to conduct future studies that continue to test specific strain combinations to assess efficacy and benefits, rather than simply growing larger or more taxonomically diverse microbial communities. Additionally, field testing of these smaller, more pointedly-chosen groups could provide valuable information to corn farmers about a biocontrol option for pathogen suppression.
Kaki P, Schlatter D and Khokhani D (2026) Refining the root-associated microbial consortia for enhanced biocontrol of the root-rot pathogen of corn. Front. Microbiol. 17:1714069. doi: 10.3389/fmicb.2026.1714069