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Colletotrichum boninense Causing Anthracnose on Coffee Trees in Brazil

In Brazil, dieback and necrosis of leaves and berries of coffee trees (Coffea arabica and C. canephora) are common symptoms of anthracnose disease caused by Colletotrichum gloeosporioides (Penz.) Sacc. In April 2010, these symptoms were observed in 100% of the plants from different coffee plantations in the Brazilian states of Espírito Santo and Bahia. Ten isolates were obtained from symptomatic leaves and berries from these areas. Of the 10 isolates, one had distinct conidial morphology with hyaline and ellipsoid conidia measuring 10 to 16 × 5.0 to 7.5 μm and melanized irregular or spatulated-shaped appressoria measuring 7.5 to 11.0 × 5.5 to 8.5 μm, formed either solitary or concatenated, which concurred with the conidia description of Colletotrichum boninense. In order to confirm the identity of this isolate, the internal transcribed spacer (ITS) rRNA region and the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene were sequenced (GenBank Accession Nos. JF683320 and JF331654, respectively) and compared to sequences from a database of C. boninense, confirming that the isolate was definitely C. boninense sensu lato, since it was exactly identical to other sequences in a large clade of isolates. To verify the pathogenicity of C. boninense in coffee and to compare the symptoms with those caused by C. gloeosporioides, leaves and berries were inoculated with the isolate of C. boninense and one representative isolate of C. gloeosporioides, both expressing the GFP (green fluorescent protein) gene. The isolates were grown for 7 days on potato dextrose agar and a conidial suspension (10⁶ conidia × ml^–1) was used to inoculate the organs, wounded and non-wounded, at different stages of development. In non-wounded organs, the conidial suspension was inoculated on the surface, and in leaves and berries used as control, the suspensions were substituted for sterile water. Leaves and berries were wounded with a sterilized needle and inoculated with 20 and 10 μl of the conidial suspension, respectively. Inoculated materials were incubated at 25°C and 100% relative humidity. The experiment was performed twice and evaluated daily for a week. No symptoms were observed on the control and non-wounded organs, while wounded organs exhibited typical anthracnose symptoms for both species. In berries, C. gloeosporioides consistently caused more severe symptoms at a faster rate than C. boninense. Both fungi caused necrosis in young but not old leaves. Typical acervuli were observed on the lesions and the fungus was successfully recovered from the inoculated tissues, which was confirmed by fluorescence microscopy, fulfilling Koch's Postulates. C. boninense has been identified as a pathogen causing anthracnose in a range of hosts worldwide. However, in Brazil, it has only been reported in pepper (Capsicum annuum) (3), passion fruit (Passiflora) (4), Hippeastrum (1) and in the medicinal plant Maytenus ilicifolia (2). To our knowledge, this is the first report of C. boninense associated with anthracnose of coffee trees in Brazil. Since the symptoms are similar to those caused by C. gloeosporioides, it can be stated that both species are associated with this disease in commercial coffee plantations in Brazil. Therefore, control strategies should consider the occurrence of C. boninense.

References: (1) D. F. Farr et al. Mycol. Res. 110:1395, 2006. (2) S. A. Pileggi et al. Can. J. Microbiol. 55:1076, 2009. (3) H. J. Tozze et al. Plant Dis. 93:106, 2009. (4) H. J. Tozze et al. Australas. Plant Dis. Notes 5:70, 2010.