Isolation and characterization of Colletotrichum coccodes from potato in Bulgaria

The fungus Colletotrichum coccodes (synonyms C. atramentarium and C. phomoides) is one of the common pathogens on vegetables of Solanaceae family. It causes fruit anthracnose of tomato, pepper and eggplant and black dot of potato. The fruit anthracnose was relatively well studied in Bulgaria but the information about potato black dot is still very scarce. The objective of this work was to characterize the isolates obtained from different potato parts (tubers, stolons, roots, stem bases) bearing microsclerotia. Conventional and molecular approaches were applied in the study. Three solid nutrient media were used for morphological and cultural description of the pathogen. For molecular investigation representative C. coccodes isolates were cultivated in potato dextrose broth. Total DNA was extracted directly from mycelium. C. coccodes-specific nested primers Cc1NF1/Cc2NR1 were used for PCR amplification. Pathogenicity test was performed on detached fruits of tomato, pepper and eggplant. All studied isolates showed morphological and cultural characteristics typical of C. coccodes although some differences were observed. PCR amplification with nested primer set gave a single specific PCR band with expected size (~350 bp) confirming the affiliation of studied isolates to C. coccodes. Pathogenicity of isolates was proven and the most pronounced symptoms were expressed on tomato fruits. C. coccodes isolates from potato were able to infect successfully other solanaceous hosts and could play a role as inoculum source for them. This should be taken into consideration in crop rotation.