European Journal of Biotechnology and Bioscience

Authors
Shivalingaiah, Umesha S

Abstract
Resistance of Oryza sativa towards X.rnoryzae pv. oryzae at different growth stages varies according tornhost genotypes as seedling resistance (at seedling stage) and adult plantrnresistance (at adult stage but susceptible at seedling stage). These stressesrncan induce biochemical and physiological changes in plants, such as physicalrnstrengthening of the cell wall through lignification, suberization and calloserndeposition by producing phenolic compounds, phytoalexins andrnpathogenesis-related (PR) proteins which subsequently prevent various pathogenrninvasions. Plants responds to bacterial pathogen attack by activating differentrndefense responses leads to accumulation of defense enzymes, inhibitors andrnantibiotics etc. which prevents the pathogen infection. Plant pathogenrninteraction is mediated by the complex network of molecular and cytologicalrnevents that determine a range between susceptibility and resistance. Peroxidisernis believed to be one of the most important factors of the plant biochemicalrndefense against pathogenic microorganism, which is actively participating inrnthe self-regulation of plant metabolism after infection. The other enzymernbelongs to this group is Polyphenol oxidase is a nuclear encoded, plastidrncopper-containg enzyme which catalses the oxygen-dependant oxidation of phenolsrnto quinines. Because of conspicuous reaction products and induction by woundingrnand pathogen attack. There are few reports of the role of polyphenol oxidase inrnplant defense against pathogens. Our studies indicate that the defense enzymesrnPeroxidase and Polyphenol oxidase are actively involved in imparting resistancernto bacterial blight in Oryza sativa varieties. It was observed that uponrninoculation of resistant seedlings, Peroxidase and Polyphenol oxidasernexpression were elevated. This may inhibit the growth of pathogen by suppressingrnattempted invasion there by imparting resistance to bacterial blight in Oryzarnsativa varieties. From these studies it appears that Peroxidase andrnPolyphenol oxidase are involved in imparting resistance to bacterial blight in Oryzarnsativa varieties. Further, Peroxidase and Polyphenol oxidase can be used asrna biochemical markers to indicate the resistance/ susceptibility nature of ricerncultivars against bacterial blight disease in Oryza sativa varieties.