Plant and Cell Physiology Advance Access published online on May 21, 2007
Plant and Cell Physiology, doi:10.1093/pcp/pcm062
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Probenazole-induced accumulation of salicylic acid confers resistance to Magnaporthe grisea in adult rice plants.
1National Institute of Agrobiological Sciences, 2-1-2 Kannondai Tsukuba, Ibaraki 305-8602, Japan, 2Miyagi Prefectural Agriculture and Horticulture Research Center, Natori Miyagi 981-1243, Japan, 3Program for Promotion of Basic Activities for Innovative Bioscience (PROBRAIN) ,
Corresponding author: Shigemi Seo. National Institute of Agrobiological Sciences (NIAS), Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan. Tel: 81-29-838-7440, Fax: 81-29-838-7469, E-mail: sseo71{at}affrc.go.jp
| Abstract |
|---|
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. Pretreatment of inoculated 4th leaves of young wild-type rice plants at 4-leaf stage with PBZ did not influence the development of whitish expanding lesions (ELs) in the susceptible interaction without the accumulation of salicylic acid (SA) and pathogenesis-related (PR) proteins. However, PBZ pretreatment increased accumulation of SA and PR proteins in the 8th 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