Journal of Integrative Agriculture ›› 2012, Vol. 12 ›› Issue (9): 1474-1484.DOI: 10.1016/S1671-2927(00)8679

• 论文 • 上一篇    下一篇

Spectroscopic Leaf Level Detection of Powdery Mildew for Winter Wheat Using Continuous Wavelet Analysis

 ZHANG Jing-cheng, YUAN Lin, WANG Ji-hua, HUANG Wen-jiang, CHEN Li-ping ZHANG Dong-yan   

  1. 1.Beijing Research Center for Information Technology in Agriculture, Beijing 100097, R.P.China
    2.Institute of Agriculture Remote Sensing and Information System Application, Zhejiang University, Hangzhou 310029, R.P.China
    3.Center for Earth Observation and Digital Earth, Chinese Academy of Sciences, Beijing 100094, R.P.China
  • 收稿日期:2011-07-11 出版日期:2012-09-01 发布日期:2012-09-09
  • 通讯作者: Correspondence WANG Ji-hua, Tel: +86-10-51503488, Fax:+86-10-51503750, E-mail: wangjh@nercita.org.cn
  • 作者简介:ZHANG Jing-cheng, Tel: +86-10-51503750, Fax: +86-10-51503750, E-mail: zjc19840222@gmail.com
  • 基金资助:

    This work was subsidized by the National Natural Science Foundation of China (41101395, 41071276, 31071324), the Beijing Municipal Natural Science Foundation, China (4122032), and the National Basic Research Program of China (2011CB311806).

Spectroscopic Leaf Level Detection of Powdery Mildew for Winter Wheat Using Continuous Wavelet Analysis

 ZHANG Jing-cheng, YUAN Lin, WANG Ji-hua, HUANG Wen-jiang, CHEN Li-ping,  ZHANG Dong-yan   

  1. 1.Beijing Research Center for Information Technology in Agriculture, Beijing 100097, R.P.China
    2.Institute of Agriculture Remote Sensing and Information System Application, Zhejiang University, Hangzhou 310029, R.P.China
    3.Center for Earth Observation and Digital Earth, Chinese Academy of Sciences, Beijing 100094, R.P.China
  • Received:2011-07-11 Online:2012-09-01 Published:2012-09-09
  • Contact: Correspondence WANG Ji-hua, Tel: +86-10-51503488, Fax:+86-10-51503750, E-mail: wangjh@nercita.org.cn
  • About author:ZHANG Jing-cheng, Tel: +86-10-51503750, Fax: +86-10-51503750, E-mail: zjc19840222@gmail.com
  • Supported by:

    This work was subsidized by the National Natural Science Foundation of China (41101395, 41071276, 31071324), the Beijing Municipal Natural Science Foundation, China (4122032), and the National Basic Research Program of China (2011CB311806).

摘要: Powdery mildew (Blumeria graminis) is one of the most destructive crop diseases infecting winter wheat plants, and has devastated millions of hectares of farmlands in China. The objective of this study is to detect the disease damage of powdery mildew on leaf level by means of the hyperspectral measurements, particularly using the continuous wavelet analysis. In May 2010, the reflectance spectra and the biochemical properties were measured for 114 leaf samples with various disease severity degrees. A hyperspectral imaging system was also employed for obtaining detailed hyperspectral information of the normal and the pustule areas within one diseased leaf. Based on these spectra data, a continuous wavelet analysis (CWA) was carried out in conjunction with a correlation analysis, which generated a so-called correlation scalogram that summarizes the correlations between disease severity and the wavelet power at different wavelengths and decomposition scales. By using a thresholding approach, seven wavelet features were isolated for developing models in determining disease severity. In addition, 22 conventional spectral features (SFs) were also tested and compared with wavelet features for their efficiency in estimating disease severity. The multivariate linear regression (MLR) analysis and the partial least square regression (PLSR) analysis were adopted as training methods in model development. The spectral characteristics of the powdery mildew on leaf level were found to be closely related with the spectral characteristics of the pustule area and the content of chlorophyll. The wavelet features performed better than the conventional SFs in capturing this spectral change. Moreover, the regression model composed by seven wavelet features outperformed (R2=0.77, relative root mean square error RRMSE=0.28) the model composed by 14 optimal conventional SFs (R2=0.69, RRMSE=0.32) in estimating the disease severity. The PLSR method yielded a higher accuracy than the MLR method. A combination of CWA and PLSR was found to be promising in providing relatively accurate estimates of disease severity of powdery mildew on leaf level.

关键词: powdery mildew, disease severity, continuous wavelet analysis, partial least square regression

Abstract: Powdery mildew (Blumeria graminis) is one of the most destructive crop diseases infecting winter wheat plants, and has devastated millions of hectares of farmlands in China. The objective of this study is to detect the disease damage of powdery mildew on leaf level by means of the hyperspectral measurements, particularly using the continuous wavelet analysis. In May 2010, the reflectance spectra and the biochemical properties were measured for 114 leaf samples with various disease severity degrees. A hyperspectral imaging system was also employed for obtaining detailed hyperspectral information of the normal and the pustule areas within one diseased leaf. Based on these spectra data, a continuous wavelet analysis (CWA) was carried out in conjunction with a correlation analysis, which generated a so-called correlation scalogram that summarizes the correlations between disease severity and the wavelet power at different wavelengths and decomposition scales. By using a thresholding approach, seven wavelet features were isolated for developing models in determining disease severity. In addition, 22 conventional spectral features (SFs) were also tested and compared with wavelet features for their efficiency in estimating disease severity. The multivariate linear regression (MLR) analysis and the partial least square regression (PLSR) analysis were adopted as training methods in model development. The spectral characteristics of the powdery mildew on leaf level were found to be closely related with the spectral characteristics of the pustule area and the content of chlorophyll. The wavelet features performed better than the conventional SFs in capturing this spectral change. Moreover, the regression model composed by seven wavelet features outperformed (R2=0.77, relative root mean square error RRMSE=0.28) the model composed by 14 optimal conventional SFs (R2=0.69, RRMSE=0.32) in estimating the disease severity. The PLSR method yielded a higher accuracy than the MLR method. A combination of CWA and PLSR was found to be promising in providing relatively accurate estimates of disease severity of powdery mildew on leaf level.

Key words: powdery mildew, disease severity, continuous wavelet analysis, partial least square regression