Analysis of resistance factor using thiophanate-methyl to control sensitive populations of Colletotrichum musae

Authors: SILVA, ANTHONY - Federal Rural University Of Pernambuco; VIEIRA, WILLIE - Federal Rural University Of Pernambuco; AMARAL, ANNA - Federal Rural University Of Pernambuco; Castlebury, Lisa; CAMARA, MARCOS - Federal Rural University Of Pernambuco

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2025
Publication Date: 3/31/2026
Citation: Silva, A.C., Vieira, W.A., Amaral, A.G., Castlebury, L.A., Camara, M.P. 2026. Analysis of resistance factor using thiophanate-methyl to control sensitive populations of Colletotrichum musae. Physiological and Molecular Plant Pathology. 142. Article e103089. https://doi.org/10.1016/j.pmpp.2025.103089.
DOI: https://doi.org/10.1016/j.pmpp.2025.103089

Interpretive Summary: Bananas are a major crop in South and Central America worth billions of dollars each year in exports to the United States and other countries, where they are a major source of a nutritious fruit. They are subject to a number of fungal plant diseases both in the field and after the harvest during shipping. Because chemicals are used to suppress plant diseases in the field and the same chemicals are used to suppress diseases during shipping, there is a danger that the pathogens could develop resistance. This study evaluated the response of one fungal pathogen to a commonly used chemical after repeated applications. In many cases, the fungus was able to develop resistance to the chemical, which would allow it to continue to cause disease in spite of being treated. This information is important for both producers and consumers as it could potentially limit the export/import of bananas for consumption around the world.

Technical Abstract: Anthracnose, caused by Colletotrichum musae, is the leading postharvest disease of banana in Brazil and occurs across all major production regions. Although thiophanate-methyl is used to control Sigatoka leaf spot, Colletotrichum populations are also frequently exposed to this fungicide in the field, resulting in strong selective pressure for resistance to benzimidazole (MBC) fungicides. This resistance threatens the long-term effectiveness of anthracnose management. To assess this risk, sixty isolates of C. musae previously classified as sensitive to thiophanate-methyl were evaluated. The isolates were transferred to Petri dishes with potato dextrose agar (PDA) medium containing concentrations of 0, 5, 10, 50, 100, 300, 500, and 1000 µg ml'¹ of thiophanate-methyl for 30 days. Seven resistant mutants were recovered, with EC50 values ranging from 114.61 to 492.53 µg ml'¹. In vivo assays on banana fruits treated at the recommended concentration (500 µg ml'¹) demonstrated poor efficacy, as resistant isolates remained pathogenic despite fungicide application. Molecular analysis of ß-tubulin codons 198 and 200 did not reveal mutations, suggesting that alternative resistance mechanisms are involved. No evidence of fitness costs was observed. Resistant and sensitive isolates did not differ significantly in mycelial growth, conidial production, conidial germination, or virulence (P > 0.05). The absence of reduced fitness suggests that resistant isolates can persist and potentially dominate field populations under continued use of thiophanate-methyl. These findings highlight the urgent need for integrated resistance management strategies, demonstrating that sole reliance on MBC fungicides is unsustainable for anthracnose control in Brazil.