First Report of Papaya (Carica papaya) Anthracnose Caused by Colletotrichum plurivorum in Mexico

Abstract

Mexico is an important papaya (Carica papaya L.) producer. In October 2014, papaya fruits cultivar Maradol with anthracnose symptoms such as sunken lesions and intense black sporulation with lighter edges were collected in Veracruz State (18°52′25″N, 96°12′2″W). The fungal culture on potato dextrose agar showed cottony greenish black colonies after 7 days. Conidia were single-celled, hyaline, cylindrical, and straight with obtuse ends, which measured 15.3 (12.2 to 18.6) × 4.5 (3.5 to 5.7) µm (n = 100). This description is similar to species Colletotrichum plurivorum (Sun et al. 2019). From a representative isolate (HP157), the internal transcribed spacer (ITS), calmodulin (CAL), β-tubulin 2 (TUB2), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) regions were amplified and sequenced (GenBank accession nos. KU522226, KU522228, KU522230, and KU522232, respectively). Basic local alignment (NCBI database) showed between 99.75 and 100% identity with sequences of C. plurivorum (accession nos. NR_160828, MG600985, and MG600781). A multilocus sequence analysis was performed from concatenated sequences using maximum likelihood with a branch support of 1,000 replicates. Phylogenetic analysis showed clustering of HP157 strain in a monophyletic clade with several C. plurivorum strains. Koch’s postulates were made on five healthy and disinfected papaya fruits cultivar Maradol. Three points per fruit were selected, and 10 µl of a spore suspension (1 × 10⁵ spores/ml) was applied. Sterilized distilled water was used in control fruits. All fruits were placed under humid conditions at 27°C for 7 days. Anthracnose symptoms appeared in all inoculated fruits, and these were similar to those observed in the field. The control fruits remained healthy. Fulfilling Koch’s postulates was confirmed with reisolation of the pathogen. C. plurivorum has been reported causing disease on papaya fruits in Japan and Taiwan (Damm et al. 2019; Sun et al. 2019). To our knowledge, this is the first report of C. plurivorum causing anthracnose of papaya in Mexico.