EFFECTS OF THE FUSARIUM-SOLANI TOXIN DIHYDROFUSARUBIN ON TOBACCO-LEAVES AND SPINACH-CHLOROPLASTS

The effects of the Fusarium solani toxin dihydrofusarubin on tobacco l eaves and on spinach chloroplasts have been studied in comparison with the herbicide methylviologen. Toxin treatment of tobacco leaves and l eaf discs resulted in a light dependent chlorophyll degradation and a simultaneous ethane production. Experiments with spinach chloroplasts showed that dihydrofusarubin interacted with the electron transport ch ain, thus forming reactive oxygen species. Experiments with DCMU and D BMIB proved that superoxide was produced on photosystem I in a light d ependent reaction. Furthermore, we showed that NADPH formation was blo cked by dihydrofusarubin. Inhibition started with 10 mu mol/L DHE wher eas about 80 % inhibition of NADP(+)-reduction was achieved with 100 m u mol/L toxin. Inhibition of NADPH-formation was accompanied by a simu ltaneous increase in ATP-production. Experiments with methylviologen p roved that the effects of the Fusarium solani toxin dihydrofusarubin o n chloroplasts were comparable with the effects of this herbicide. The significance of the dihydrofusarubin toxin for symptom development on citrus trees infected with Fusarium solani is discussed.