Study On The Antibacterial Mechanism Of Ethoxylated Chloranil Against Rice Bacterial Leaf Streak Pathoge

The bacterial leaf streak（BLS）of rice caused by Xanthomonas oryzae pv.oryzicola（Xoc）infesting rice is a very serious bacterial disease.Ethylicin,an analogue of allicin,is a broad-spectrum bactericide developed by the Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences.Its activity was measured in the preliminary stage of this thesis,and the results showed that ethylicin had good inhibition activities against Xoc both in vivo and in vitro.However,the mechanism of bacterial inhibition of ethylicin against Xoc is not clear.Therefore,this thesis intends to investigate the mechanism of bacterial inhibition by ethylicin against Xoc under in vivo and in vitro conditions.The specific findings are as follows.1.The effect of ethylicin on the control of BLS was determined in a live pot experiment using 200μg/mL concentration,and the results showed that the protective and curative activities of ethylicin against BLS were 49.86%and 45.65%,which were significantly higher than those of thiodiazole copper（43.81%and 39.71%）.The changes of hydrogen peroxide,defense enzymes and defense genes in rice leaves were also measured,and the results showed that ethylicin can increase hydrogen peroxide production,defense enzyme activity and relative expression of defense genes in rice leaves.2.The in vitro inhibitory activity of ethylicin was determined by turbidimetric method against Xoc,and the results showed that ethylicin had very good inhibitory activity against Xoc with an EC₅₀ of 2.12μg/mL,which was significantly better than that of zinc thiazole（22.57μg/mL）,bismerthiazol（55.29μg/mL）,and thiodiazole copper（72.15μg/mL）.3.In this thesis,we investigated the physiological and biochemical effects of ethylicin on Xoc.The results showed that ethylicin affected the intact morphology of Xoc as observed by scanning electron microscopy,and that ethylicin inhibited the swarming effect of Xoc by effectively suppressing the extracellular polysaccharide production,biofilm formation,and extracellular enzyme production of Xoc to reduce the pathogenicity of Xoc.4.The proteomic results showed that,among them,a total of 2754 proteins were detected in Xoc treated with low concentrations of ethylicin,of which 17 significantly different proteins,2 up-regulated proteins and 15 down-regulated proteins were identified.Combined with KEGG and GO enrichment analysis,the two oxidative phosphorylation pathway proteins（ACU12＿RS13405 and ACU12＿RS13355）that most likely affected Xoc virulence were identified.They were also validated using quantitative real-time polymerase chain reaction（RT-qPCR）.