Caracterización fenotípica, molecular, patogénica y sensibilidad a fungicidas de aislados de Colletotricum spp causantes de la antracnosis del mango en México

Abstract

La antracnosis, causada por Colletotrichum spp., es la enfermedad pre- y postcosecha más importante del mango a nivel mundial y es controlada principalmente mediante el uso de fungicidas pertenecientes a las clases metil-benzimidazol-carbamatos (MBC), inhibidores externos de la quinona (QoI) e inhibidores de la demetilación (DMI). En México, esta enfermedad se ha asociado únicamente a C. gloeosporioides y C. asianum. En este estudio, se utilizó caracterización fenotípica, patogénica y análisis de secuencias Apn2/MAT IGS para identificar a las especies de Colletotrichum responsables de causar la antracnosis del mango en México. Adicionalmente, se determinó la sensibilidad in vitro a fungicidas MBC (benomil y carbendazim), QoI (azoxystrobin y kresoxim-metil) y se estimó la sensibilidad base al procloraz (DMI), en 100 aislados Colletotrichum colectados de 2010 a 2013 en huertos comerciales de mango distribuidos en los principales estados productores de México. La caracterización morfológica y cultural indicó que todos los aislados pertenecieron al complejo de especies de Colletotrichum gloeosporioides. El análisis filogenético reveló que C. dianesei, C. asianum, C. tropicale y C. fructicola son las especies asociadas a esta enfermedad. Así mismo, las pruebas de patogenicidad en frutos de mango mostraron que todos los aislados indujeron la enfermedad. Los aislados presentaron valores de concentración efectiva a la cual se inhibe 50% del crecimiento micelial (CE50) que variaron de 0.1123 a 0.3543, de 0.0880 a 0.1792, de 0.0016 a >1000, de 0.0335 a >1000 y de 0.0048 a 0.0851 µg mL-1 para benomil, carbendazim, azoxystrobin, kresoxim-metil y procloraz, respectivamente. Estos resultados mostraron alta sensibilidad a fungicidas MBC y DMI en especies de Colletotrichum causantes de la antracnosis del mango en Mexico. Sin embargo, se detectó la existencia de aislados altamente resistentes a fungicidas QoI en huertos de mango de México. Los datos determinados en este estudio permitirán monitorear variaciones posteriores en la sensibilidad de poblaciones de Colletotrichum de mango a fungicidas MBC, QoI y DMI. _______________ PHENOTYPIC, MOLECULAR, AND PATHOGENIC CHARACTERIZATION AND FUNGICIDE SENSITIVITY OF Colletotrichum SPECIES CAUSING MANGO ANTHRACNOSE IN MEXICO. ABSTRACT: Anthracnose, caused by Colletotrichum spp., is the most important pre- and postharvest disease of mango worldwide and is controlled primarily by fungicides belonging to Methyl Benzimidazole Carbamates (MBC), Quinone outside inhibitors (QoI) and Demethylation inhibitors (DMI) classes. In Mexico, only C. gloeosporioides and C.asianum have previously been associated to this disease. In this study, phenotypic and pathogenic characterizations as well as Apn2/MAT IGS sequence-data were used to identify the Colletotrichum species causing mango anthracnose in Mexico. During the years 2010-2013, a total of 100 Colletotrichum isolates were obtained from mango tissues with anthracnose symptoms across the major mango production areas in Mexico. All isolates were screened for sensitivity to MBC (benomyl and carbendazim) and QoI (azoxystrobin and kresoxim-methyl) fungicides and tested to determine their baseline sensitivity to prochloraz. Isolates were tested using an in vitro assay to determine the effective fungicide concentration at which 50% of mycelial growth was inhibited (EC50) for each isolate-fungicide combination. Based on morphological and cultural characteristics, all isolates were identified in the C. gloeosporioides species complex. While, the phylogenetic analysis generated from Apn2/MAT IGS sequences revealed that C. dianesei, C. asianum, C. tropicale and C. fructicola were associated with symptoms of mango anthracnose. Pathogenicity tests on mango fruits showed that all isolates from this study could induce anthracnose lesions. EC50 values ranged from 0.1123 to 0.3543, 0.0880 to 0.1792, 0.0016 to >1000, 0.0335 to >1000 and from 0.0048 to 0.0851 µg mL-1 for benomyl, carbendazim, azoxystrobin, kresoxim-methyl and prochloraz, respectively. Our results revealed the existence in Mexico of species of Colletotrichum from mango that are highly sensitive to benomyl, carbendazim and prochloraz. Also, we determined the presence of resistance to QoI fungicides in species of Colletotrichum from mango in Mexico. The data obtained here will serve to monitor future variations in sensitivities of Colletotrichum populations from mango to MBC, QoI and DMI fungicides.