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Use of stomatal conductance and chlorophyll fluorescence as diagnostic tools for the prompt detection of brown root rot pathogen
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  • Kenichi Yazaki,
  • Fuku Kimura,
  • Chunhua Zhang,
  • Delphis Levia,
  • Mitsuteru Akiba,
  • Shin-Taro Saiki,
  • Atsushi Ishida,
  • Mikiko Kojima,
  • Yumiko Takebayashi,
  • Hitoshi Sakakibara,
  • Yutaka Maruyama,
  • Yuko Ota,
  • Norio Sahashi
Kenichi Yazaki
Forestry and Forest Products Research Institute Hokkaido Research Center

Corresponding Author:[email protected]

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Fuku Kimura
Nihon University College of Bioresource Sciences Graduate School of Bioresource Sciences
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Chunhua Zhang
Forestry and Forest Products Research Institute
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Delphis Levia
University of Delaware
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Mitsuteru Akiba
Forestry and Forest Products Research Institute Kyushu Research Center
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Shin-Taro Saiki
Forestry and Forest Products Research Institute
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Atsushi Ishida
Kyoto University
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Mikiko Kojima
RIKEN
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Yumiko Takebayashi
RIKEN Plant Science Center
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Hitoshi Sakakibara
RIKEN
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Yutaka Maruyama
Nihon University College of Bioresource Sciences Graduate School of Bioresource Sciences
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Yuko Ota
Nihon University College of Bioresource Sciences Graduate School of Bioresource Sciences
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Norio Sahashi
Forestry and Forest Products Research Institute
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Abstract

Brown root rot, caused by infection of the basidiomycete Phellinus noxius (Corner) G. Cunn., threatens trees in forests, orchards and plantations of tropical regions. Here, we demonstrate the use of stomatal conductance and chlorophyll fluorescence as diagnostic tools for the early detection of brown root rot using artificially inoculated seedlings of two tree species of different functional types, semi-deciduous Bischofia javanica Blume and evergreen Rhaphiolepis umbellata (Thunb.) Makino. Stomatal closure seemed to be the primary reaction to root decay, without either species exhibiting a decrease in root hydraulic conductance associated with hyphae invasion or change in stem water potential. The parameters of chlorophyll fluorescence showed linear responses to hyphae invasion. The Calvin cycle as well as the amount of carbohydrates and abscisic acid were all altered in relation to hyphal invasion of the roots, with extent of change depending on species. These physiological responses were detected earlier than the appearance of visible disease symptoms. Although there were some differences in chlorophyll fluorescence response between the two species, our results have demonstrated that prompt measurements of stomatal conductance and chlorophyll fluorescence can be used for the early detection of the infection of brown root rot.