P-325 - Exploring Tar Spot Microbiome Variation: A meta-analysis of sequencing data

Tar spot disease has been reported in most corn-producing countries in the Americas, representing a severe risk for production. Multiple organisms have been reported in tar spot lesions but only a few have been identified and described. Sequence data have allowed the identification of new organisms in tar spot lesions across different locations. However, results between studies show inconsistencies due to differences in the genomic region sequenced, sequencing methods, software and databases used. The objective of this meta-analysis is to quantify variation among tar spot microbiomes and analyze the phylogenetic relationships among the organisms present in each location. The sequencing data generated by three microbiome studies from 2019 to 2024 were analyzed in QIIME2 using the UNITED database published in 2025. The variation among tar spot microbiomes depends primarily on the sampled location, however, the clustering method, taxonomic classifier and pipeline used to analyze data affected the relative abundance of some organisms such as Paraphaeosphaeria and Fusarium, which can lead to misinterpretations. Taxonomic nomenclature has also impacted the presence of organisms such as Neottiosporina and Coniothyrium creating confusion about their abundance. The total number of OTUs for Phyllachora, Microdochium, and Paraphaeosphaeria are 250, 150 and 130, respectively, based on ITS2. These OTUS are clustered into clades based on their locations. Analyzing tar spot microbiomes provides a better understanding of the organisms present and their potential impact on disease severity.