FIRST REPORT OF COLLETOTRICHUM GRAMINICOLA ON SOUTHERN SWEET-GRASS LEAVES IN POLAND

Abstract

Southern sweet-grass (Hierochloe australis) is a perennial tuft-grass the leaves of which are used for aromatization of alcohol and tobacco products (Przybyl et al., 2011). In 2013 oblong, irregular lesions surrounded with reddish-brown ring, as well as yellow, reddish brown discoloration were observed in Warsaw-Wilanow on H. australis leaves. Black acervuli with setae were only noted around necrotic spots. Seven isolates of the fungus were obtained on PDA from infected leaves. Cultures were black-gray with aerial white mycelium. Conidia were hyaline, 1-celled, lunate to falcate 22.4x4.4 μm in size. All isolates produced melanized appressoria. Linear growth of isolates was measured on PDA, Czapek solution agar, CMA, MEA and SNA at 24°C. The best growth of the fungus after10 days incubation was observed on PDA (73 mm in diameter) and the slowest on SNA (34 mm). To fulfill Koch's postulates each of isolates was used to inoculate healthy, 30-day-old seedlings of H. australis by placing a drop of a conidial suspension on their leaves (10 plants/isolate). The leaf surface had previously been disinfected with 1% sodium hypochlorite. Inoculated plants were sealed in foil bags and incubated at 24°C. Symptoms appeared after 5 days. Isolates obtained from artificially inoculated leaves had the same morphology as those used for inoculation. The internal transcribed spacer (ITS) region of the fungus was amplified using the primers ITS1/ITS4 (Hsiang and Goodwin, 2001) and sequenced (GenBank accession Nos. KM040784, KM040785). BLAST analysis of sequences showed 99% homology to Colletotrichum graminicola. To our knowledge, this is the first report of C. graminicola on H. australis. So far, in Poland this pathogen was only found on maize (Korbas, 2006) and bentgrass (Pronczuk, 2000).