Pomegranate (Punica granatum L.) is an important crop in Greece. In 2010, fruits of the pomegranate cv. Wonderful, in commercial fields located in the Prefecture of Komotini in eastern Greece, were observed to have symptoms of distinct dark brown spots. The waxy acervuli observed in infected tissue were subepidermal, typically with setae and simple, short, erect conidiophores. Conidia were hyaline, one celled, ovoid to oblong, slightly curved or dumbbell shaped, and 10 to 15 μm long and 5 to 7 μm wide. The pathogen was isolated on acidified potato dextrose agar (PDA) (2.5 ml of 85% lactic acid per liter of nutrient medium) and incubated at 23°C for 7 days. The pathogen was identified as Colletotrichum gloeosporiodes (Penz) Sacc. on the basis of morphological characteristics and internal transcribed spacer (ITS) sequence (100% identity to AJ301912, C. gloeosporioides species complex) (3) by CBS Fungal Biodiversity Centre, Identification Service, Utrecht, the Netherlands, (CG-1 isolate deposited in CBS Collection; Accession No. CBS 129372). Koch's postulates were completed in the laboratory by placing a 40-μl drop of suspension (4 × 105 conidia ml–1 of water) on a wounded area of healthy fruits of cv. Wonderful. Fruits were surface sterilized by dipping in 0.1% chlorine solution and allowed to dry in a laminar flow hood. There were 15 inoculated and 15 control fruits (similarly sprayed with sterile distilled water) in a randomized design. Fruits were covered with perforated polythene bags to maintain a high humidity necessary for infection that were removed 48 h after inoculation and the fruits were maintained at room temperature (23 ± 2°C). Lesion development was recorded daily for each fruit. Koch's postulates were satisfied after reisolating the fungus from inoculated fruit that developed symptoms similar to those observed on fruits collected from fields. To our knowledge, this is the first report of the occurrence of C. gloeosporioides as a causal agent of fruit spot of pomegranates in Greece. Fruit spots caused by C. gloeosporioides have been reported in pomegranate fields of other countries around the world (1,2).
References: (1) B. K. M. Lakshmi et al. Trop. Agric. Res. 22:183, 2011. (2) D. S. Patel. Indian Phytopathol. 62:252, 2009. (3) B. S. Weir and P. R. Johnston. Mycotaxon 111:209, 2010.