Antibacterial Activity Of The Active Constituents Separated From Mahonia Fortunei And Its Control Effect On Rice Bacterial Leaf Streak Disease

Mahonia fortunei is a kind of common medicinal and ornamentals plant, and it is abundant in resources in China. Preliminary studies showed that the extract from Mahonia sp. displayed excellent inhibitory activity against Xanthomonas bacteria, but there is no report about the study of Mahonia fortunei extract in controlling plant diseases caused by Xanthomonas bacteria. In this study, Xanthomonas oryzae pv.oryzicola was used as target for isolating and purifying the inhibition activity compounds from Mahonia fortunei, and the monomer compound microemulsion was developed. Simultaneously, suitable fungicides were screened to make mixture, and the control effect of the compound and its mixture on rice bacterial leaf streak was evaluated by means of pot tests. The main results can be briefly described as follows:1.257.12g methanol extract was got from 10kg M. fortunei stalk powder by using impregnation method. Two high-purity compounds were isolated from methanol extract by acid-alkali precipitation, silica column chromatography, thin-layer chromatography(TLC) and recrystallization method. Based on the spectral data analyses, the antibacterial compounds were identified as berberine and jatrorrhizine, respectively. The EC50 experiments showed that berberine possessed a higher inhibitory activity against X.oryzae pv. oryzicola with EC50 of 2.9008 mg/L, better than jatrorrhizine with EC50 of 16.0533 mg/L.2. The inhibitory activities of the M. fortunei methanol extract and berberine against 19 plant pathogenic fungi and 13 bacteria were determined with mycelium growth rate method and inhibition zone method, respectively. Extract and berberine possessed a broad antimicrobial spectrum, and had noticeable inhibitory action on Bipolaria maydis, Curvularia lunata,X. oryzae pv. oryzae and X. oryzae pv. oryzicola.3. The formulation of 1% berberine microemulsion was determined as follows:1% berberine,20% methanol,5% N,N-Dimethylformamide(DMF),5% Dimethyl sulfoxide (DMSO),9.6% agricultural emulsifier 0202-C,2.4% calcium dodecylbenzenesulfonate, and 5% 1,3-butylene glycol,5% ethylene glycol,48% water. The mixture had the strongest inhibiting effect on Xanthomonas oryzae pv. oryzicola when the mass ratio of berberine and quinoline copper reaches 7:1.4. There were no significant difference between the control efficiency of berberine on rice bacterial leaf streak at the concentration of 0.1 g/L and 20% bismerthiazol WP in the active ingredient of 0.44g/L; The pot tests showed that berberine performed well in prevention and treatment on rice bacterial leaf streak. Moreover, it had a long persistence in the rice plants, and it could transport well from the front of rice leaves to back, the top to bottom and the bottom to top, but poor in transverse transporting capacity.5. The control effect of the mixture on rice bacterial leaf streak at the concentration of 0.1 g/L was higher than that of single dose of berberine and 20% bismerthiazol WP in active ingredient of 0.44g/L, but failed to reach the significant difference. When the concentration increased to 0.5 g/L, the mixture showed significantly higher control effect on rice bacterial leaf streak than 20% bismerthiazol WP in the active ingredient of 0.44g/L.