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Journal of General Plant Pathology

, Volume 69, Issue 1, pp 17–22 | Cite as

Ratio of rice reflectance for estimating leaf blast severity with a multispectral radiometer

  • Takashi Kobayashi
  • Eiji Kanda
  • Shigeo Naito
  • Toshihiko Nakajima
  • Ichiro Arakawa
  • Kazutoshi Nemoto
  • Masanao Honma
  • Hiroyuki Toujyou
  • Kiyoshi Ishiguro
  • Katsuki Kitada
  • Yoichi Torigoe
FUNGAL DISEASE

Abstract

 Rice reflectance was measured to determine the spectral regions most sensitive to leaf blast infection with a multispectral radiometer. As disease severity increased, reflectance also increased in the 400–500 nm (blue), 570–700 nm (red), and 900–2000 nm regions but decreased in the 500–570 nm and 700–900 nm regions. The increased reflectance in the blue and red regions may be attributed to decreased chlorophyll and carotenoid contents in response to the blast infection. The maximum and minimum reflectance differences occurred at 680 nm and 760 nm for the nondiseased and diseased rice, respectively. The spectral location of maximum sensitivity was 675 nm regardless of disease severity. Rice reflectance ratios were evaluated as indicators of leaf blast severity. Two ratios, R550/R675 (reflectance at 550 nm divided by reflectance at 675 nm), and R570/R675 quantified the significant disease severity. These wavelengths were selected based on the sensitivity minima and maxima. The ratios of nondiseased rice plants varied depending on growth stage. The variation in ratios must be considered when they are used to estimate leaf blast severity.

Key words Magnaporthe grisea Multispectral radiometer Remote sensing Rice leaf blast Spectral reflectance 

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Copyright information

© Springer-Verlag Tokyo 2003

Authors and Affiliations

  • Takashi Kobayashi
    • 1
  • Eiji Kanda
    • 1
  • Shigeo Naito
    • 1
  • Toshihiko Nakajima
    • 2
  • Ichiro Arakawa
    • 2
  • Kazutoshi Nemoto
    • 2
  • Masanao Honma
    • 2
  • Hiroyuki Toujyou
    • 2
  • Kiyoshi Ishiguro
    • 1
  • Katsuki Kitada
    • 3
  • Yoichi Torigoe
    • 1
  1. 1.National Agricultural Research Center for Tohoku Region, Morioka 020-0198, JapanJP
  2. 2.Fukushima Prefectural Agricultural Experiment Station, Koriyama, JapanJP
  3. 3.Nakanihon Air Service Co., Aichi, JapanJP

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