engleski

Biological characterization of Fusarium graminearum Schw. isolated from different host plants

A large number of Fusarium species with different frequencies in isolations, therefore of unequal significance for wheat, participate in diseases ethiology. According to our previous research (1, 2) and results obtained by other authors (5, 3) F. graminearum is the most frequent species and strongly aggressive toward cereals, especially to wheat. F. graminearum strains were isolated during the years 1996-1999 from different hosts: wheat (6), barley (1) and maize (3) seed, wheat root (1), maize stem (1), maize (5) and wheat (4) debris and Capsella bursa-pastoris (2). F. graminearum strains were isolated from plants tissue in moist chambers at 20ºC under 12 h dark/light regime. Developed fungal colonies were examined under stereo microscope. Conidia or mycelium tip was transferred on PDA, CLA, Bilai or water agar and subcultured at 5ºC, 15ºC, 20ºC, 25ºC and 30ºC. Diameter colonies, presence of aerial mycelium, sporulation and size of macroconidia were measured after 3, 5 and 8 days. Pathogenicity of the strains was examined according to the methods described by Mesterhazy (4) on two winter wheat cultivars. The study has shown that there are no significant differences between strains in all examined characteristics expect pathogenicity. The fastest development of mycelium was recorded on all types of agars at both 20C and 25C. After an eight day period, sporulation of all isolates sub-cultured on to PDA was very weak or there were no sporulating colonies at all. A larger number of sporulating colonies were obtained after 21-28 days (12h dark/light regime), which corresponds with the data provided by extensive literature published on this subject. With regard to the isolates sub-cultured on to CLA, more sporulating colonies were obtained, despite the fact that the aerial mycelium was not particularly lush (the medium being water agar). Pathogenicity test showed that F. graminearum isolates had been strongly, even very strongly pathogenic to wheat seedlings. Seed germination of wheat Cv. 1 was 26.67% and there were 75% of seedlings with necrosis of radicle. On the other hand, seed germination of wheat Cv. 2 was 53.33%, whereas there were 43.75% of seedlings with necrosis of radicle. It was established that all tested isolates from maise residues were weakly pathogenic, the incidence of which was > (%) in germinating seeds and < (%) of seedlings with necrosis of radicle. The isolate 1Aw4 from grain of wheat may be described as extremly pathogenic, while other isolates from grains of wheat as well as all other tested isolates may be said to be strongly pathogenic to wheat seedlings.

Fusarium graminearum; hosts; biological characterization

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