Tar spot susceptibility of corn influences phyllosphere-associated bacterial and fungal microbiomes

Authors: Singh, Raksha; SIC-HERNANDEZ, WILY - Purdue University; Crane, Charles; SHIM, SU - Purdue University; TELENKO, DARCY - Purdue University; Goodwin, Stephen

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2025
Publication Date: 10/7/2025
Citation: Singh, R., Sic-Hernandez, W.R., Crane, C.F., Shim, S., Telenko, D.E., Goodwin, S.B. 2025. Tar spot susceptibility of corn influences phyllosphere-associated bacterial and fungal microbiomes. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2025.1581312.
DOI: https://doi.org/10.3389/fmicb.2025.1581312

Interpretive Summary: Tar spot, caused by the obligate fungal pathogen Phyllachora maydis, is a foliar disease of corn that has become a major economic concern in the United States, yet little is known about other microbes that might interact with this organism on corn leaves or how they might affect disease development. To fill this knowledge gap, DNA sequences were obtained from bacteria and fungi growing on or in leaves collected from 16 inbred lines of corn that differed in severity of tar spot symptoms from resistant to susceptible. The results showed that infection of corn by P. maydis may result in a distinct microbial community with fewer species of bacteria and fungi and lower diversity of fungi. Several potentially beneficial bacteria and fungi were identified on the tolerant lines that could help to manage tar spot severity in the future. These results will be of interest to plant pathologists trying to control tar spot disease and to ecologists for a better understanding of the interactions among microbes on corn leaves.

Technical Abstract: Tar spot, caused by the obligate fungal pathogen Phyllachora maydis, is a foliar disease of corn that has become a major economic concern in the United States. We investigated phyllosphere microbiomes in relation to corn inbreds with differential tar spot symptoms under natural P. maydis infestation in the field. Leaf samples from sixteen inbred lines were assessed for tar spot symptoms, and bacterial and fungal microbiomes were characterized by paired-end sequencing on the Illumina MiSeq platform. Comparison of the phyllosphere microbiomes revealed distinct bacterial and fungal communities between tolerant and susceptible lines. Bacterial and fungal species richness was significantly higher in tolerant compared to susceptible inbred lines in a sample-specific manner. In contrast, there were no clear differences in diversity when including evenness of bacterial communities between the tolerant and susceptible lines. Diversity of fungal communities differed significantly, particularly between six of the fourteen susceptible lines versus tolerant lines. Plant-beneficial bacterial genera such as Methylorubrum and Quadrisphaera were associated with tolerant lines, while Pantoea, Deinococcus and Pseudomonas were the least abundant. Fungal genera Cladosporium, Papiliotrema, Cryptococcus, Tilletiopsis and Alternaria were associated with tolerant lines while Sphaerellopsis was the least-abundant genus. In contrast, Puccinia, Sphaerellopsis and Phyllachora were the dominant fungal genera in susceptible lines. Our findings imply that P. maydis infection may result in a distinct microbiota with lower diversity. Further analyses of these distinct microbiota between tolerant and susceptible lines could lead to a better understanding of the potential role of foliar microbiomes in resisting P. maydis infection.