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  • Author or Editor: P. Vidhyasekaran x
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The effect of elicitors isolated from the mycelial walls of Colletotrichum falcatum (the red rot pathogen of sugarcane) and from C. lindemuthianum (a non-pathogen) in suspension-cultured cells of sugarcane was studied. Both the elicitors induced the synthesis of enzymes of the phenyl­propanoid pathway such as PAL, TAL and 4CL and also resulted in the enhanced accumulation of phenolics. However, a specific induction of the defense parameters at higher levels was recorded in suspension cells treated with the pathogen elicitor and no such differential response was observed in the case of the non-pathogen elicitor. Elicitor induced necrosis and browning of cells were observed which suggests an additional evidence that elicitors simulate pathogen infection and thus provide a valuable reason that study on elicitor induced responses may be useful in understanding the host defense mechanisms against the red rot pathogen at molecular level.

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Changes in activities of phenylalanine ammonia-lyase,chitinase,ß-1,3-glucanase and phenolic content in rice leaves were measured at different times after treatment of leaves with Pseudomonas fluorescens strain Pf1.When rice leaves were sprayed with P.fluorescens,substantial increase in the phenylalanine ammonia-lyase activity was observed 1 day after treatment.Following increase of the first enzyme of the phenylpropanoid pathway,phenolic content of rice leaves also increased to a maximum at 4 days after P.fluorescens treatment.Chitinase activity increased in rice leaves in response to application of P.fluorescens and the maximum enzyme activity was observed 3 days after treatment.ß-1,3-Glucanase activity also increased significantly from 1 day after P.fluorescens treatment and continued to increase through 7 days.A five-fold increase in glucanase activity was observed 7 days after P.fluorescens treatment.

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An elicitor molecule has been separated from Macrophomina phaseolina, the root rot pathogen of mungbean (Vigna radiata). Cell cultures of mung­bean cultivars one resistant and another susceptible to the pathogen, which responded to the elicitor have been established. The elicitor treatment induced rapid increases in phenolic synthesis, activation of phenylalanine ammonia-lyase and peroxidase in the cultured cells. Relative increases in phenolic synthesis and peroxidase activity were observed in suspension-cultured cells of the resistant cultivar compared to that of the susceptible one due to elicitor treatment.

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Authors: R. M. Babu, R. Velazhahan, P. Vidhyasekaran, K. Seetharaman and A. Sajeena

Systemic acquired resistance induced by benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH) in rice against bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae was studied. Rice plants (IR 50) pre-treated with BTH showed resistance to a challenge infection with Xanthomonas oryzae pv. oryzae. About 50% reduction in disease intensity was observed in plants treated with BTH at 100 µg a.i./ml. Immunoblot analysis using barley chitinase antiserum revealed the induction of a 35 kDa chitinase in rice in response to treatment with BTH. The results indicate that the BLB resistance can be induced even in genetically susceptible cultivar through application of BTH.

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