| Rice bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most serious rice diseases worldwide. Zn thiazole as an organic zinc compound began to be used for the prevention and treatment of rice leaf blight. Little bioassay and molecular studies of Zn thiazole was conducted.In this article, studies were done as follows:(1) Biological activities of zinc thiazole against Xanthomonas oryzae pv. oryzae;(2) Characterization of zinc thiazole resistance of Xanthomonas oryzae pv. oryzae;(3)Rice response to zinc thiazole against Xanthomonas oryzaepv. oryzae;(3)Preliminarily study for mechanism of action of zinc thiazole;The toxicity in vitro and the biological activity of zinc thiazole in vivo against Xoo were preliminarily studied. The results showed that the EC50 value of zinc thiazole to the bacteria in vitro was (90.17±4.66)μg/mL. It may be related to difficultly soluble in the solvent of zinc thiazole. Besides,strain 2-1-1 which is resistant to bismerthiazol can not be detected resistant to bismerthiazol and zinc thiazole in vitro. Protective and curative effect of zinc thiazole against bacterial leaf blight of rice was assayed in vivo, and the EC50 values were 22.9 and 52.4 μg/mL for curative and protective activity, respectively, suggesting the curative activity of zinc thiazole was better than that of protective activity. And the EC50 values of bismerthiazol were 64.8 and 50.6 μg/mL for curative and protective activity, suggesting the protective activity of bismerthiazol was better than that of curative activity. It showed that there were no different resistant between strains. That means there exist similarity in resistance mechanism between zinc thiazole and bismerthiazol. In addition, zinc thiazole could be absorbed by roots and leaves of rice and exhibited upward movement characteristics from the application site. No in vitro resistant strains of Xoo against zinc thiazole were obtained through repeated ultraviolet light induction. Three in vivo resistant strains of Xoo against zinc thiazole were obtained through bismerthiazol training. The resistant strains lost their resistance through 10 times transfers on NA plates and one time transfer in vivo. In vitro, the inhibitory activity of zinc thiazole to in vivo resistant strains was not different to sensitive strain. Resistant mutants of Xoo were detected by screening with zinc thiazole in vivo, and the resistance mutant frequency was 13.3%. There was positive cross-resistance between zinc thiazole and bismerthiazol in Xoo. However, the resistance of these mutants was relatively low and not stable after 10 transfers on zinc thiazole-free medium subcultures. It showed that the mechanism of zinc thiazole and bismerthiazol perhaps was identical in vivo. In conclusion,the inhibitory activity to Xoo of zinc thiazole is better than that of growth activity. Zinc thiazole can be used for controlling Xoo with a low resistance risk.The rice would produce some harmful substances after introduction of outside factors. The results showed that the H2O2 and PAL activities in rice increased highly after dealling with zinc thiazole. This may improve the plant resistance for external environmental factors better. And the SOD activity in rice was not changed. Chorophyl B in rice increased highly after dealing with zinc thiazole Id. The expression of genes PR1 and PAL decreased after dealing with zinc thiazole. It inferred that it may improve the plant resistance for external environmental factors better.The results showed that turbidity of strain ZJ173 increased significantly by adding 60 UM and 180 UM Vbl in MM nutrient agar. It proved that under Vbl may offset the medicinal properties of zinc thiazole. It showed that there existed antagonism between Vbl and bioactivity of zinc thiazole. With the increasing of the concentration of Vbl,the length of the disease spot decreased. And the length of the disease spot increased after adding zinc thiazole. It indicated the antagonism between Vbl and bioactivity of zinc thiazole again. With the increasing of the concentration of Vbl,the content of H2O2 increased. It showed that Vb could enhance the defense response of rice. It was similar to previous conclusions that the length of the 2-1-1 disease spot decreased with the increasing of the concentration of Vbl. There existed cross-resistant between Vbl and zinc thiazole. The main genes that play a role during the synthetic route of Vb are THIG,THIE and THID. What’s more,the gene expression of resistant stains and sensitive strains is total different.Therefore,it concluded that the mechanism of action of zinc thiazole is related to the synthetic route of Vb. But further study is still necessary. |
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