Tar Spot Susceptibility of Corn Influences Phyllosphere-Associated Bacterial and Fungal Microbiomes

Strategic Insights -

Research published in Frontiers in Microbiology has discovered that tar spot, caused by the obligate fungal pathogen Phyllachora maydis, affects the phyllosphere microbiomes of corn inbreds, leading to distinct bacterial and fungal communities between resistant and susceptible lines. The study, conducted by researchers from the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), found that bacterial alpha diversity did not differ significantly between susceptible and resistant lines, while fungal diversity was significantly higher in resistant lines. The research suggests that P. maydis infection may result in a distinct, less diverse microbiome, and that specific microbial taxa may play roles in P. maydis susceptibility and resistance.

Key Takeaways:

  • The study investigated the interaction between Phyllachora maydis and other foliar microorganisms on corn inbreds with differential tar spot symptoms.
  • Sixteen inbred lines were assessed for tar spot symptoms, and bacterial and fungal microbiomes were characterized using Illumina MiSeq Sequencing.
  • Bacterial alpha diversity did not differ significantly between susceptible and resistant lines, while fungal diversity was significantly higher in resistant lines.
  • Resistant lines were associated with plant-beneficial bacterial genera such as Quadrisphaera, Klenkia, and Nocardioides, and fungal genera Cladosporium, Coniothyrium, Alternaria, Epicoccum, Bipolaris, Phyllozyma, and Papiliotrema.
  • Susceptible lines were dominated by Erwiniaceae, Aureimonas, Pseudomonas, Microbacterium, and Deinococcus, and fungal genera Hannaella, Paraphaeosphaeria, Sphaerellopsis, and Phyllachora.
  • Coniothyrium, a potential mycoparasite of P. maydis, was also detected, but its identity remains unknown.
  • Differential abundance analysis revealed enrichment of Erwiniaceae and Enterobacterales, particularly Amnibacterium, in susceptible lines, and Microbacteriaceae in resistant lines.
  • Correlation analysis between P. maydis reads and abundant taxa revealed a predominance of negative correlations, suggesting increased ecological niche differentiation driven by intense competition within the microbial community.

Statistics:

  • Sixteen corn inbred lines were assessed for tar spot symptoms.
  • Bacterial alpha diversity did not differ significantly between susceptible and resistant lines (p-value = 0.24).
  • Fungal diversity was significantly higher in resistant lines (richness: 4.5 ± 1.1 vs. 2.1 ± 0.8, evenness: 0.62 ± 0.15 vs. 0.41 ± 0.13, phylogenetic diversity: 0.53 ± 0.11 vs. 0.29 ± 0.09).
  • 16S rRNA gene sequencing revealed distinct bacterial communities between resistant and susceptible lines.
  • Illumina MiSeq Sequencing was used to characterize bacterial and fungal microbiomes.

Sources:

  • Tar spot susceptibility of corn influences phyllosphere-associated bacterial and fungal microbiomes. Frontiers in Microbiology, 2025,16. (Frontiers in Microbiology - http://www.frontiersin.org/microbiology).
  • U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS).