The baseline sensitivity of Botrytis cinerea to fenpyrazamine was evaluated using 323 isolates collected in Japan prior to its launch. In this study, the isolates were classified as “sensitive” and “low-sensitive” according to their mycelial growth on 10 mg/L fenpyrazamine. However, their EC50 values for the germ-tube elongations from conidia were not significantly different between these two classes. In both a pot test and a field trial, diseases caused by the sensitive and low-sensitive isolates were effectively controlled by fenpyrazamine.
Flutianil, chemically characterized as a cyano-methylene thiazolidine, showed antifungal activity against powdery mildew on various crops but not any other plant pathogens tested. Flutianil showed high residual and translaminar activities and rainfastness against Podosphaera xanthii. It also exhibited curative activity against P. xanthii on cucumber at an extremely low concentration of 10 mg/L. There was no cross-resistance between flutianil and other existing fungicides. Morphological studies revealed that flutianil did not inhibit the early infection behavior of Blumeria graminis f. sp. hordeii.e., conidium bursting, primary and appressorial germinations, appressorium development and hook formations, but it did inhibit haustorium formation and further fungal development. Nutrient absorption by haustoria and subsequent secondary hyphal elongation was inhibited by flutianil but not by the fungicide that showed a similar inhibitory pattern up to the haustorium formation stage of the infection process. These findings suggest that flutianil might have a novel mode of action.
Glutathione transferase (GST) is an important class of detoxification enzymes that are vital for defense against various xenobiotics and cellular oxidative stress. Previously, we had reported an unclassified glutathione transferase 2 in Bombyx mori (bmGSTu2) to be responsible for detoxifying diazinon. In this study, we aimed to identify the amino acid residues that constitute a hydrogen-bonding network important for GST activity. Site-directed mutagenesis of bmGSTu2 suggested that residues Asn102, Pro162, and Ser166 contribute to its catalytic activity.