Cloning and characterization of a laccase gene from Ganoderma spp. causing basal stem rot disease in coconut

Basal stem rot disease in coconut is caused by the white-rot fungus Ganoderma lucidum, which is soilborne in nature. Its degree of virulence is governed by the activity of the laccase enzyme. Of twenty-five isolates belonging to the genus Ganoderma obtained from different host species, the isolate from Silent Valley (SV) showed the greatest laccase activity in vitro, followed by the isolate from Veppankulam (CRS-1). These two isolates also reacted positively in the laccase assay in vitro. The laccase-positive SV and CRS-1 isolates were further amplified by polymerase chain reaction (PCR) using degenerate primers for the partial sequence, which showed the fragment size of 200 bp. The highly virulent SV isolate was cloned in a plasmid vector and sequenced. It was confirmed as a partial-length laccase gene and submitted to the GenBank database. The nucleotide sequence of the DNA of this isolate showed high homology with those of the laccase genes of other basidiomycetes

«Pseudomonas fluorescens» mediated antifungal activity against «Rhihzoctonia solani» causing sheath blight in rice

Antifungal activity of Pseudomonas fluorescens strains PF1, FP7 and PB2 was tested against the rice sheath blight pathogen Rhizoctonia solani. The bacterial strains produced antibiotic 2,4-diacetyl phloroglucinol, iron chelating siderophore, hydrogen cyanide, lytic enzymes, such as chitinase and β-1,3-glucanase in culture, and induced chitinase in plants. Soaking R. solani sclerotia in either bacteria-free culture filtrates or in sap extracted from plants treated with Pseudomonas strains PF1 and FP7 or inoculated with R. solani significantly reduced the germination capacity of the sclerotia. The inability of treated sclerotia to cause sheath blight symptoms indicated loss of virulence. In all the experiments strain PF1 or FP7 always performed better than PB2. The 35 kDa chitinase induced by Pseudomonas in rice plants was purified and its antifungal activity against mycelium and sclerotia of R. solani was demonstrated. The production of antibiotics, antifungal compounds, bacterial lytic enzymes and the induction of plant chitinase were correlated with antifungal activity against R. solani sclerotia

Understanding the molecular basis of plant growth promotional effect of Pseudomonas fluorescens on rice through protein profiling

<p>Abstract</p> <p>Background</p> <p>Plant Growth Promoting Rhizobacteria (PGPR), <it>Pseudomonas fluorescens </it>strain KH-1 was found to exhibit plant growth promotional activity in rice under both <it>in-vitro </it>and <it>in-vivo </it>conditions. But the mechanism underlying such promotional activity of <it>P. fluorescens </it>is not yet understood clearly. In this study, efforts were made to elucidate the molecular responses of rice plants to <it>P. fluorescens </it>treatment through protein profiling. Two-dimensional polyacrylamide gel electrophoresis strategy was adopted to identify the PGPR responsive proteins and the differentially expressed proteins were analyzed by mass spectrometry.</p> <p>Results</p> <p>Priming of <it>P. fluorescens</it>, 23 different proteins found to be differentially expressed in rice leaf sheaths and MS analysis revealed the differential expression of some important proteins namely putative p23 co-chaperone, Thioredoxin h- rice, Ribulose-bisphosphate carboxylase large chain precursor, Nucleotide diPhosphate kinase, Proteosome sub unit protein and putative glutathione S-transferase protein.</p> <p>Conclusion</p> <p>Functional analyses of the differential proteins were reported to be directly or indirectly involved in growth promotion in plants. Thus, this study confirms the primary role of PGPR strain KH-1 in rice plant growth promotion.</p

Induction of systemic resistance in rice by leaf extracts of Zizyphus jujuba and Ipomoea carnea against Rhizoctonia solani

Plants accumulate a great diversity of natural products, many of which confer protective effects against phytopathogenic attack. Earlier we had demonstrated that the leaf extracts of Zizyphus jujuba and Ipomoea carnea inhibit the in vitro mycelial growth of Rhizoctonia solani, and effectively reduce the incidence of sheath blight disease in rice.7 Here we demonstrate that foliar application of the aqueous leaf extracts of Z. jujuba and I. carnea followed by challenge inoculation with R. solani induces systemic resistance in rice as evident from significantly increased accumulation of pathogenesis-related proteins such as chitinase, β-1,3-glucanase and peroxidase, as well as defense-related compounds such as phenylalanine ammonia-lyase and phenolic substances. Thin layer chromatographic separation of secondary metabolites revealed presence of alkaloid and terpenoid compounds in the leaf extracts of Z. jujuba that exhibited toxicity against R. solani under in vitro condition. Thus, the enhanced sheath blight resistance in rice seedlings treated with leaf extracts of Z. jujuba or I. carnea can be attributed to the direct inhibitory effects of these leaf extracts as well as their ability to elicit systemic resistance against R. solani