Studies On The Mode Of Action Of Wuyiencin

Wuyiencin is a nucleotide antibiotic produced by Streptomyces ahygroscopicus var. wuyiensis. In this research, the inhibition and the mode of action of wuyiencin against Botrytis cinerea as well as other pathogens were characterized. The effect of this antibiotic on the activity of four resistance-related enzymes in tomato seedlings were also studied. The results include:1. Wuyiencin exhibited an inhibitory ability to 14 species of phytopathogenic fungi and 3 species of bacteria (1 pathogen and 2 non-pathogens). Botrytis cinerea was more sensitive to the antibiotic than the other microorganisms.2. Wuyiencin inhibited the growth of hyphae and the germination of conidia of B. cinerea and the value of 50% effective concentration (EC50) was 18.0 g/ml and 14.1 g/ml, respectively. It could completely inhibit the germination of conidia of B. cinerea when the concentration of wuyiencin reached 100 g/ml. The pathogenicity of hyphae and conidia of B. cinerea treated with wuyiencin ( 10 g/ml) was significantly attenuated. Microscopic observation showed that wuyiencin could interfer the normal development of hyphae of B. cinerea by the increased formation of branches and hyphal vacuoles. Leakage of cytoplasm from hyphal tips of B. cinerea treated with wuyiencin at 100 g/ml was also observed. Germ tubes of B. cinerea treated with wuyiencin at 75 g/ml were constricted in shape.3. Wuyiencin was detected to influence on the permeability of the cell membrane of B. cinerea as shown by the increased electric conductivity in the cultural filtrates of the pathogen. However, it had no effect on sterol biosynthesis of this fungus. With 3H-glucosamine, 3H-adenine and 14C-glutamate as the precursors, incorporation experiments showed that wuyiencin significantly inhibited the protein synthesis, but had no significant effect on the synthesis of nucleic acid and chitin of B. cinerea.4. The increased activities of superoxide dismutase, peroxidase, polyphenol oxidase and phenylalanine ammoniam-lyase in tomato seedlings upon the treatment by wuyiencin at 100 g/ml were detected. This suggests that wuyiencin could trigger the defense reactions of tomato plants.A conclusion can be made that wuyiencin is a potential biofungicide for the control of B. cinerea as it not only can inhibit the pathogen directly, but also induce the resistance of tomato.