Colletotrichum brevisporum causing anthracnose of papaya (Carica papaya L.) in Mexico

Abstract

Papaya fruit cv. Maradol showing typical symptoms of anthracnose were observed in a commercial orchard located in the municipality of Pinotepa Nacional at the coastal region of Oaxaca, Mexico in September 2020. The incidence rate of anthracnose reached 60%. The symptoms consisted of sunken, water-soaked lesions with salmon-coloured conidia masses on the surface of papaya fruit. The aim of this study was to identify the causal agent of papaya anthracnose based on the phylogenetic analysis of four concatenated datasets. The isolate exhibited sparse white to greyish aerial mycelium and clearly shaped concentric rings with exudate of orange conidia on potato dextrose agar. The fungus was identified as Colletotrichum brevisporum using sequence data of the internal transcribed spacer (ITS) region, and part of the actin (act), glyceraldehyde-3-phosphate dehydrogenase (gapdh), and chitin synthase (chs-1) genes. The fungus isolated from diseased fruit produced lesions on wounded fruit and unwounded fruit. The pathogen was re-isolated from lesions on inoculated fruit to fulfill Koch’s postulates. To our knowledge, this is the first report of C. brevisporum causing anthracnose disease on papaya fruit in Mexico.