Molecular identification and characterization of Colletotrichum sp. isolates from Tahiti lime, tamarillo, and mango

Anthracnose is a very limiting disease affecting production, as well as postharvest quality of numerous fruit crops in Colombia. The current management practices for this disease are partially effective due to limited information about the etiology, the inoculum sources, population structure and variation of the pathogen. A total of 293 Colletotrichum isolates were obtained from symptomatic tissues collected from Tahiti lime, tamarillo and mango orchards. To determine the Colletotrichum species causing the symptoms, amplification, and PCR product analysis for intergenic regions of the ribosomal DNA were conducted. Genetic diversity of the fungal population was assessed with Random Amplified Microsatellites (RAMS). Results of this study indicated that anthracnose in Tahiti lime and tamarillo are caused by Colletotrichun acutatum whereas symptoms on mango were induced by the species Colletotrichum gloeosporioides, which was also fund in few

citrus samples. RAMS data analysis indicated the existence of two distinct species groups, with a low similarity index (35%). RAM profiles also showed a clear host differentiation of isolates. The C. acutatum population originated from tamarillo exhibited a narrow and homogeneous genetic base, while the C. acutatum population from Tahiti lime was more heterogeneous and  genetically complex, as determined by the analysis of molecular variance (AMOVA) and of Ni-Li coefficient. The C. gloeosporioides population originated from mango and Tahiti lime was heterogeneous and highly diverse, with clear host differentiation according to RAM profiles. Collectively, the results from this study provide new insight into the general characteristics of Colletotrichum populations on various hosts; this type of knowledge will prove useful in designing more effective management practices.