Identification and molecular characterisation of Colletotrichum species from avocado, citrus and pawpaw in Ghana

Abstract

Owing to previous identifications based solely on morphological characteristics, the identity of the causal agents of anthracnose disease of pawpaw and avocado in Ghana is in doubt. In addition, the pathogen has not been identified previously on citrus. In this study, isolates of the pathogen were obtained from anthracnose lesions on avocado and pawpaw, and atypical anthracnose lesions on citrus. The isolates were identified using PCR with species-specific primers, complemented by phylogenetic analysis of nucleotide sequences of the internal transcribed spacer region and partial glyceraldehyde-3-phosphate dehydrogenase gene. The pathogenicity of the isolated fungi was determined on detached matured fruits. All isolates, including those isolated from citrus, were identified as Colletotrichum gloeosporioides from the expected 480 bp PCR products amplified by PCR. The phylogenetic analysis showed that isolates from avocado and pawpaw were C. siamense, rather than C. gloeosporioides, whereas isolates from citrus were C. gloeosporioides sensu stricto. The pathogens were able to induce disease only on wounded mature fruits.