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Colletotrichum simmondsii Causing Anthracnose on Safflower in the Czech Republic

Safflower (Carthamus tinctorius L.) is an oil crop that is suitable for dry growing conditions in the Czech Republic. Most of the Czech production is used as bird feed. Typical anthracnose symptoms were observed at one safflower field in the Moravia Region of the Czech Republic during the 2005 growing season. Since then, the disease has become widespread with 100% yield losses observed in several locations in 2009. Symptoms consisted of circular spots on leaves and stem blight characterized by dark-colored stem lesions bearing salmon-colored conidia masses in acervuli. A fungus was isolated from symptomatic safflower plants (cv. Sabina) on potato dextrose agar and incubated at 25°C as described by Kwon et al. (3). The color of fungal colonies changed from white to gray with age with salmon-orange pigmentation on the reverse side of plates. Similar observations had been reported by Jelev et al. (1). Conidia were colorless, fusiform, and measured 10 to 17 μm (mean 13.59) × 4 to 8 μm (mean 5.98). Morphology suggested a Colletotrichum sp. To fulfill Koch' postulates, safflower plants at the BBCH 12 growth stage (second leaf fully expanded) were spray inoculated with a conidia suspension (1 × 10⁵ conidia/ml). Growth chamber conditions were temperature 20 ± 1°C, relative humidity 70 ± 5%, with a 16-h photoperiod. Control plants were treated with sterile distilled water. Typical anthracnose symptoms were observed 1 week after inoculation. Control plants were symptomless. The pathogen was reisolated from infected stems and leaves. PCR with primers CaInt2 and ITS4 was used to confirm the identification of a Colletotrichum sp. Reaction products obtained with these primers were approximately 500 bp long. The ribosomal DNA internal transcribed spacer region containing ITS1, 5.8S, and ITS2 of the isolate from safflower was sequenced and identified with the BLASTn program. The sequence matches with 100% similarity to the sequence of the Glomerella acutata teleomorph of Colletotrichum acutatum (GenBank Accession No. AB548282) and 100% similarity to C. simmondsii (GenBank Accession No. GU183359). C. acutatum and C. simmondsii can be distinguished from each other by pigment color (4), with the safflower isolate matching the description of C. simmondsii. Kim et al. (2) recorded C. acutatum on safflower fields in the Euiseong area of Korea in 1997. To our knowledge, this is the first report of C. simmondsii causing safflower anthracnose in the Czech Republic.

References: (1) Z. J. Jelev et al. Plant Dis. 92:172, 2008. (2) W. G. Kim et al. Plant Pathol. J. 15:62, 1999. (3) J. H. Kwon et al. Plant Pathol. J. 15:172, 1999. (4) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.