Journal Article

Probenazole-Induced Accumulation of Salicylic Acid Confers Resistance to <i>Magnaporthe grisea</i> in Adult Rice Plants

Takayoshi Iwai, Shigemi Seo, Ichiro Mitsuhara and Yuko Ohashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 7, pages 915-924
Published in print July 2007 | ISSN: 0032-0781
Published online July 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm062
Probenazole-Induced Accumulation of Salicylic Acid Confers Resistance to Magnaporthe grisea in Adult Rice Plants

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Probenazole (PBZ) is the active ingredient of Oryzemate, an agrochemical which is used for the protection of rice plants from Magnaporthe grisea (blast fungus). While PBZ was reported to function upstream of salicylic acid (SA) in Arabidopsis, little is known about the mechanism of PBZ-induced resistance in rice. The role of SA in blast fungus resistance is also unclear. The recommended application period for Oryzemate is just before the Japanese rainy season, at which time rice plants in the field have reached the 8-leaf stage with adult traits. Thus, the involvement of SA in PBZ-induced resistance was studied in compatible and incompatible blast fungus–rice interactions at two developmentally different leaf morphology stages. Pre-treatment of inoculated fourth leaves of young wild-type rice plants at the 4-leaf stage with PBZ did not influence the development of whitish expanding lesions (ELs) in the susceptible interaction without the accumulation of SA and pathogenesis-related (PR) proteins. However, PBZ pre-treatment increased accumulation of SA and PR proteins in the eighth leaves of adult plants at the 8-leaf stage, resulting in the formation of hypersensitive reaction (HR) lesions (HRLs). Exogenous SA induced resistance in adult but not young plants. SA concentrations in blast fungus-inoculated young leaves were essentially the same in compatible and incompatible interactions, suggesting that PBZ-induced resistance in rice is age-dependently regulated via SA accumulation.

Keywords: Blast fungus; Disease resistance; Plant age; Probenazole; Rice; Salicylic acid

Journal Article.  5368 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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