Screening for antimicrobial activities in some plant extracts

Methanol-extracts from nine plant species were screened for their bioactivity against Peronophythora litchii,Xanthomonas oryzae pv.oryzae and Ralstonia solanacearum.The plant extracts were applied on detached litchi young leaves before inoculation with sporangial suspension of P.litchii.The results showed that methanol extracts(at conc.of 100mg dry methanol extract weight per mL) of Hamamelis mollis and Derris scabricanlis possessed the highest antifungal activity against litchi downy blight with the inhibitory effectiveness of 88.89%,followed by Phryma leptostachya(77.78%),Clematis armcmdii(66.67%),and Daphniphyllum macropodum(61.11%).At the dose of 1mg dry methanol extract weight,none of the tested plant methanol extracts showed inhibitory activities against X.oryzae pv.oryzae,whereas,H.mollis had the strongest antibacterial activity against R.solanacearum with the inhibitory zone diameter of 21 mm,followed by Aristolochia mollissima,D.macropodum,Pachyrhizus erosus,Vicia unijuga,and C.armcmdii with the inhibitory zone diameter between 9 to 11 mm.