Involvement of catalase and superoxide dismutase in resistance of Botrytis cinerea to dicarboximide fungicide vinclozolin

In order to examine whether defensive enzymes are related to the resistance of Botrytis cinerea to dicarboximide fungicides, catalase (CAT) and superoxide dismutase (SOD) activities were compared in a dicarboximide-susceptible (DS) isolate and a dicarboximide-resistant (DR) isolate of B. cinerea. Tn the absence of vinclozolin, the DR isolate had 1.5- and 3.0-fold higher CAT and SOD activities, respectively, than the DS isolate. When the DR isolate was incubated with 2 mu M vinclozolin, CAT and SOD activities were considerably enhanced at 1 h after the fungicide treatment and then decreased to the level of their respective control. In the DS isolate, however, such changes of the enzyme activities were not significant. Native polyacrylamide gel electrophoresis and activity staining of CAT and SOD revealed that both enzymes had two isoforms and that the staining intensities of the isoforms were different in the DS and the DR isolates. Both isoforms of CAT appeared to have higher staining intensity in the DR isolate than in the DS isolate, whereas one isoform of SOD was more preferentially distinct in the DR isolate. The enhanced isoform of SOD in the DR isolate was found to be Cu,Zn-SOD. When the DR isolate was incubated with 2 mu M vinclozolin, both isoforms of CAT from the DR isolate tended to become slightly more apparent at 1 h after the fungicide treatment, bur their staining activity was slightly reduced after the prolonged treatment of the fungicide. No such changes of the staining intensity were observed in the CAT isoforms from the DS isolate and in the SOD isoforms either from the DS or from the DR isolate. Our results demonstrate that the DR isolate has enhanced activities of CAT and SOD regardless of the presence of vinclozolin. They also show that a much higher amount of the Cu,Zn-SOD isoform exists in the DR isolate than in the DS isolate. Therefore, it can be concluded that enhanced activities of CAT and SOD, mostly of Cu,Zn-SOD, at least partly confer the resistance of B. cinerea to the dicarboximide fungicides. (C) 1997 Academic Press.