Abstract

Phytotoxic components detected by a bean (Vicia faba) leaf assay were isolated from extracts of dried mycelia and liquid culture filtrates of Drechslera wirreganensis and D. campanulata by preparative thin layer chromatography. Mass spectrometric examination of chromatographically homogeneous phytotoxic fractions was consistent with the presence of cytochalasin B and dihydrocytochalasins in both fungi. Cytochalasin B was present at 10.3 g/kg dry weight of the mycelium for D. wirreganensis and 7.7 g/kg for D. campanulata. In addition, differences were observed in the minor cytochalasin components. In D. wirreganensis, a more hydrophobic cytochalasin derivative with an ion at m/z 675 was present. In D. campanulata a component of similar hydrophobicity was present, but with an ion at 481 m/z. Measurable inhibition of wheat seed germination by cytochalasin B was observed only at or above 70 μM in 1% dimethyl sulfoxide solution. The formation of bi-nucleate cells, a common feature in mammalian cells treated with cytochalasin B, is reported in barley root tips. Differences in lesion morphology caused by these two related pathogenic fungi are also associated with differences in types and amounts of the phytotoxic components they produce.