Isolation and identification of the fungus Colletotrichum cordylinicola causing anthracnose disease on Cordyline fruticosa in Florida.
Imported Hawaiian Ti Cordyline plants (Cordyline fruticosa) 'Tipsy Pink' with anthracnose symptoms were found in Gainesville, FL, in 2013. A Colletotrichum spp. was isolated from symptomatic Cordyline plants and Koch's postulates were fulfilled. The colony color on acidified potato dextrose agar (PDA) was orange with slight shades of pink and light gray aerial mycelium. Sclerotia and setae were absent. Conidia were one-celled, hyaline, guttulate, and cylindrical with round ends. The mean size of the conidia was 14.7×5.0 µm and ranged from 12.5 to 17.5×3.8 to 7.5 µm. Polymerase chain reaction (PCR) was performed on the internal transcribed space (ITS) and 28S rDNA regions of the isolate, and the sequences were compared with those of Colletotrichum spp. in GenBank. Sequence analysis indicated that the isolate belonged to C. cordylinicola. This is the first report of C. cordylinicola on C. fruticosa in Florida and the United States. Anthracnose symptoms developed on healthy-looking, latently infected Hawaiian Ti plants within 2 to 3 months, and 34% to 44% of the non-inoculated plants became diseased in 3 months. Reactions of several Dracaena and Cordyline species and varieties including Hawaiian Ti to C. cordylinicola were assessed. Several Dracaena and Cordyline species and varieties including Hawaiian Ti exhibited a differential response when inoculated with C. cordylinicola, but none of them was resistant. Hawaiian Ti was the most and lucky bamboo (Dracaena sanderiana) the least susceptible [area under the disease progress curve (AUDPC)=71 vs. 10 cm2.d-1] to C. cordylinicola. The slope of the log-transformed disease progress regression line was steepest on Hawaiian Ti and D. marginata variety 'Colorama' plants, intermediate on varieties 'Tarzan' and 'Magenta', and least on lucky bamboo [slope=0.046, 0.044, 0.036, and 0.034 vs. 0.020 log(cm2+1)/d, respectively, with a mean se of 0.0006].