Differences among fungal microbiomes associated with tar spot of corn in Ecuador, Guatemala, and Indiana

Authors: SIC, WILY - Purdue University; GRIBSKOV, MICHAEL - Purdue University; ACOSTA, ALEX - Purdue University; CRUZ, ANDRES - Purdue University; CRUZ, CHRISTIAN - Purdue University; Goodwin, Stephen - Steve

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2024
Publication Date: 6/17/2024
Citation: Sic, W., Gribskov, M., Acosta, A., Cruz, A., Cruz, C.D., Goodwin, S.B. 2024. Differences among fungal microbiomes associated with tar spot of corn in Ecuador, Guatemala, and Indiana. Meeting Abstract. https://doi.org/na.

Interpretive Summary: N/A

Technical Abstract: Tar spot of corn is a recently emerged disease in the USA and Canada, with a broad geographic distribution in Central, South, and North America. This disease is caused by the obligate pathogen Phyllachora maydis and is associated with Monographella maydis (syn. Microdochium maydis) and Coniothyrium phyllachorae in Mexico, but not in the United States. M. maydis was initially considered to cause fish-eye lesions and C. phyllachorae was described as a mycoparasite of P. maydis, but their presence and roles in tar spot disease are still unclear. Fungal microbiomes associated with tar spot lesions can be influenced by multiple factors such as geographic location, environmental conditions, and corn cultivar. To test the hypothesis that fungal communities present in tar spot lesions differ by location, we collected tar spot-diseased leaves in Indiana, Guatemala, and three regions in Ecuador with different environmental conditions. A secondary goal was to test whether Coniothyrium and Monographella are present in locations with different environmental conditions than Indiana, where they so far have not always been detected. The alpha and beta diversity analyses showed a clear distinction between fungal microbiomes in Ecuador, Guatemala, and Indiana; samples from the same location clustered together. The most abundant taxa in the three countries are P. maydis, Paraphaeosphaeria, and Sordariomycetes incertae sedis, with high similarity to Microdochium. In Ecuador, Pharaphaeospaeria is mostly present in the highlands and almost absent in the Amazon region. In Guatemala, P. maydis was the most abundant taxon in two locations but was almost absent in a third. The frequency of Coniothyrium in all locations was less than one percent. Our results show that the composition of fungal communities associated with tar spot is determined by geographic location, and that Microdochium likely plays a significant role in disease development in Ecuador and Guatemala.