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Mexican Journal
of Phytopathology

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  • Phytopathological note

Fungal causal agents of the Black Spot of the cactus (Opuntia ficus-indica) in Colima, Mexico

By Zoila Lizbeth Chavarría Cervera, Andrés Quezada Salinas, Pedro Valadez Ramírez, Wilberth Chan Cupul, Jesús Enrique Castrejón Antonio, Juan Carlos Sánchez Rangel*

* Corresponding Author. Email: / Institution: Universidad de Colima

Accepted: 06/March/2024 – Published: 02/April/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2401-2

Abstract Background/Objective. The prickly pear cactus (Opuntia ficus-indica) holds significant economic, social, and cultural importance in Mexico. However, it is recurrently affected by Black Spot disease (BS), caused by various phytopathogenic fungi. Identifying the causal agents of BS in commercial prickly pear crops is crucial for efficient agronomic management of the disease. The objective of this study was to identify the phytopathogenic fungi responsible for BS in prickly pear plantations in the Colima state, Mexico.

Materials and Methods. Fifty cladodes from 50 plants exhibiting BS symptoms were collected from commercial plantations in Colima. The pathogenicity of the isolated fungi was verified using Koch’s postulates, and those causing the most severe BS symptoms were molecularly identified.

Results. Thirty-five fungi were isolated from plants with BS symptoms, of which 20 exhibited distinct mycelial growth. Only six fungi induced BS symptoms; three of them were responsible for severe symptoms in cladodes: Alternaria alternata, Corynespora cassiicola, and Neoscytalidium dimidiatum.

Conclusion. BS is caused by various phytopathogenic fungi, but this is the first report of C. cassiicola and N. dimidiatum as causal agents of BS in prickly pear cactus

Keywords: Corynespora, Neoscytalidium, Alternaria, pathogenicity, ITS

Figure 1. Plants and cladodes with symptoms of Black Spot in vegetable prickly pear cactus (O. ficus-indica) crops in various plantations in Colima state, Mexico. A) El Espinal, B) Agua Dulce, C) Las Guásimas, D) Juluapan
Figure 1. Plants and cladodes with symptoms of Black Spot in vegetable prickly pear cactus (O. ficus-indica) crops in various plantations in Colima state, Mexico. A) El Espinal, B) Agua Dulce, C) Las Guásimas, D) Juluapan
Figure 2. Fungi isolated from prickly pear cactus cladodes showing symptoms of Black Spot. The isolates are deposited in the mycological collection of the Faculty of Biological and Agricultural Sciences at the University of Colima for subsequent morphological and molecular characterization.
Figure 2. Fungi isolated from prickly pear cactus cladodes showing symptoms of Black Spot. The isolates are deposited in the mycological collection of the Faculty of Biological and Agricultural Sciences at the University of Colima for subsequent morphological and molecular characterization.
Figure 3. Fungi isolated from cladodes with Black Spot symptoms that induced severe lesions in the pathogenicity test. Growth on PDA of <em>Alternaria alternata</em> (obverse, A; reverse B) and symptoms induced on the cladode (E), <em>Corynespora cassiicola</em> (D, E, F), and <em>Neoscytalidium dimidiatum</em> (G, H, I).
Figure 3. Fungi isolated from cladodes with Black Spot symptoms that induced severe lesions in the pathogenicity test. Growth on PDA of Alternaria alternata (obverse, A; reverse B) and symptoms induced on the cladode (E), Corynespora cassiicola (D, E, F), and Neoscytalidium dimidiatum (G, H, I).