PJB-2013-214
CHARACTERIZATION OF CULTURE FILTRATES OF PSEUDOMONAS SYRINGAE PV. SESAMI AND XANTHOMONAS CAMPESTRIS PV. SESAMI ISOLATES ASSOCIATED WITH SESAME BACTERIAL BLIGHT
SYEDA SADIQA FIRDOUS1*, REHANA ASGHAR2 AND M. IRFAN-UL- HAQUE3
Abstract
Different bioassays were used to detect secondary metabolites produced by Pseudomonas syringae pv. sesami (Psse) and Xanthomonas campestris pv. sesami (Xcs) virulent isolates. The bioassays were antibacterial activity, phytotoxic activity, potato tuber outgrowth and seedling assay that included qualitative, semi quantitative and quantitative. In qualitative assay, phytotoxic activity of cell free culture filtrates of Psse-1, Psse-2and IBD-1 of Xcs isolates were applied on non host plant brinjal and host sesame leaves and symptoms were observed. Psse-2 isolate elicited water soaking and chlorosis symptoms on both tested plants as produced by pathogen, while Psse-1 showed only water soaking and necrosis symptoms. Psse-2 isolate only induced hypertrophy outgrowth in potato tuber discs, neither Psse-1 nor IBD-1 isolate induces this outgrowth on potato tuber discs. Antibacterial activity was also checked against three pathogenic bacteria such as Salmonella sp., Pseudomonas sp., and an unknown bacterial pathogen. Results showed that Psse-1 and Xcs isolate showed inhibition zones against only unknown bacterial pathogen but Psse-2 isolate did not exhibit any such zones against the tested bacterial pathogens. Moreover, biological effects of different concentrations of culture filtrates of Psse and Xcs isolates on sesame susceptible and resistant seedlings showed that all tested culture filtrates illustrated sesame root and shoot inhibition, while the inhibition recorded was more against Psse-2 isolate culture filtrate than others. Xcs and Psse-1 showed less inhibition and effective at 70 and 100% concentrations. Over all inhibition was less in tolerant than susceptible genotypes. Present results showed that Psse isolates produced two different classes of toxins, chlorosis as well as necrosis. Chlorosis inducing toxins did not show antibacterial activity but could be detected in potato tuber discs bioassay. On the other hand, necrosis inducing toxin showed antibacterial activity against unknown bacterial pathogen. Seedling bioassay also shown that chlorosis inducing toxin was more effective in inhibition of seedlings then necrosis production toxin.
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