Pathogenicity of Fusarium graminearum isolated from cultivated plants and weeds to wheat seedlings

F. graminearum Schw. (Gibberella zaeae (Schw.) Petch) is spread in all wheat, barley and maize growing areas (Kommedahl et al. 1979, Hill et al. 1983, Leslie et al. 1990, Diaz de Ackermann et al. 1996, Chakaeva 2000, Kryuchkova et al. 2002), and in Croatia it is a dominant agent of root rot and head blight of wheat and barley (Tomasovic 1993, Cosic 1997, Jurkovic et al. 1998). Isolations of F. graminearum were made from wheat, barley, maize and 7 weed species (Cirsium arvense, Amaranthus hybridus, Daucus carota, Urtica dioica, Sorghum halepense, Lamium purpureum, Capsella bursa-pastoris) collected during a nine-year period (1996-2004) from ten locations in Croatia. A total of 50 isolates of F. graminearum were used in testing their pathogenicity to wheat seedlings (cv. Demetra). Pathogenicity test was performed on 23 isolates from wheat (14 from grains, 9 from debris), 2 isolates from barley grains, 11 isolates from maize (2 from grains, 1 isolate from stem, 8 from debris) and 14 isolates from weeds (3 isolate from C. bursa-pastoris and S. halepense, 2 isolates from U. dioica, A. hybridus and C. arvense, 1 isolate from L. purpureum and D. carota). Procedure was described by Mesterhazy (1978). It is known that all isolates of one Fusarium species do not exhibit the same degree of pathogenicity to one particular plant species, nonetheless to several different hosts. During our researches, it was determined that the majority of investigated isolates were very to extremely pathogenic to wheat seedlings, and only few isolates were classified as being of middle pathogenicity. Pathogenicity test showed that isolates from weeds were equally pathogenic to wheat seedlings as the isolates from cultivated plants. Germination of wheat grains infected with isolates from weeds was 40% - 70%. Of the total number of germinated grains, there was the germ root necrosis determined in 33.33% - 72.22% of cases.