Multilocus identification and thiophanate-methyl sensitivity of Colletotrichum gloeosporioides species complex associated with fruit with symptoms and symptomless leaves of mango |
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Authors: | Dionicio Fuentes-Aragón Vladimiro Guarnaccia Angel Rebollar-Alviter Sandra B. Juárez-Vázquez Fortino Aguirre-Rayo Hilda V. Silva-Rojas |
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Affiliation: | 1. Posgrado de Fitosanidad, Campus Montecillo, Colegio de Postgraduados, Texcoco, Estado de México, Mexico;2. Department of Agricultural, Forest and Food Sciences, University of Torino, Grugliasco, TO, Italy;3. Centro Regional Morelia, Universidad Autónoma Chapingo, Morelia, Michoacán, Mexico Posgrado en Protección Vegetal, Departamento de Parasitología Agrícola, Universidad Autónoma Chapingo, Texcoco, Estado de México, Mexico;4. Posgrado en Protección Vegetal, Departamento de Parasitología Agrícola, Universidad Autónoma Chapingo, Texcoco, Estado de México, Mexico;5. Departamento de Ingeniería en Agronomía, Instituto Tecnológico de Ciudad Altamirano, Guerrero, Mexico;6. Producción de Semillas, Campus Montecillo, Colegio de Postgraduados, Texcoco, Estado de México, Mexico |
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Abstract: | Colletotrichum spp. are known causal agents of anthracnose in a broad host range, causing severe losses. Currently, the most effective way to reduce disease is by fungicide application, which could give rise to resistant populations. This study aimed to determine the Colletotrichum species present in conventional and organic mango orchards and to evaluate their pathogenicity and sensitivity to the benzimidazole fungicide thiophanate-methyl. Seventy-one isolates from fruit with symptoms and symptomless leaves were obtained. From these, 20 representative morphotypes were analysed based on glyceraldehyde-3-phosphate dehydrogenase partial gene sequencing. A subset of 10 isolates based on different species, isolation source, and fungicide sensitivity was used for morphological and multilocus phylogenetic analysis. Colletotrichum queenslandicum was only identified in conventional production systems, C. chrysophilum only in organic systems, and C. asianum and C. siamense in both. Pathogenicity tests showed all species were pathogenic, and only C. asianum caused symptoms via both unwounded and wounded inoculation methods. Overall, 25.3% of isolates (n = 18) that belong to C. siamense, isolated from a conventional orchard, grew on thiophanate-methyl amended media at 1,000 µg/ml, suggesting high resistance. Resistance was not correlated with any common point mutations at positions 198 and 200 of the β-tubulin 2 protein, as commonly found in other fungal pathogens resistant to benzimidazole. The 74.7% remaining isolates (n = 53) belonging to the other species were sensitive, reaching 100% inhibition at <10 µg/ml. Even with benzimidazole application, anthracnose symptoms persist due to the emergence of pathogenic Colletotrichum subpopulations that are resistant to thiophanate-methyl. |
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Keywords: | Colletotrichum spp. fungicide resistance mango anthracnose phylogenetic analysis point mutations |
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