Abstract
This study examined the effect of different bactericides and fungicides on oospore germination of Aphanomyces iridis. The results obtained are as follows. (1) Oospores can be divided into morphologically complete and incomplete oospores under a light microscope. (2) Both corn meal decoction (CMD) and FOWLES's defined liquid (FDL) media are suitable for producing many complete oospores. (3) Complete oospores with high germinability can be obtained after growing the fungus on either CMD or FDL medium for 2 weeks at 25°C. (4) Optimum temperature and pH for oospore germination are 25°C and about 6.4, respectively. (5) No inhibitory action of oospore germination is usually seen when chloramphenicol, streptomycin sulfate and vancomycin are used at concentrations up to 100, 80 and 400 ppm, respectively, although the latter two are both sometimes inhibitory at 20-40 and 100 ppm. (6) Amphotericin B, benomyl and iprodione inhibit oospore germination at concentrations higher than 5, 0.5 and 50-100 ppm, respectively. Benomyl is highly inhibitory even at 0.5-1 ppm. Metalaxyl inhibits at the intermediate concentrations used and thiophanatemethyl inhibits at the concentrations higher than 10-50 ppm.
