中国农业科学 ›› 2022, Vol. 55 ›› Issue (6): 1110-1126.doi: 10.3864/j.issn.0578-1752.2022.06.005

• 耕作栽培·生理生化·农业信息技术 • 上一篇    下一篇

基于成像高光谱的小麦冠层白粉病早期监测方法

蔡苇荻(),张羽,刘海燕,郑恒彪,程涛,田永超,朱艳,曹卫星,姚霞()   

  1. 南京农业大学农学院/国家信息农业工程技术中心/智慧农业教育部工程研究中心/农业农村部农作物系统分析与决策重点实验室/江苏省信息农业重点实验室/现代作物生产省部共建协同创新中心,南京 210095
  • 收稿日期:2021-05-25 接受日期:2021-09-06 出版日期:2022-03-16 发布日期:2022-03-25
  • 通讯作者: 姚霞
  • 作者简介:蔡苇荻,E-mail: 2019101180@njau.edu.cn
  • 基金资助:
    国家重点研发计划(2021YFE0194800);民用航天技术预先研究项目(D040104);国家自然科学基金(31971780);江苏省重点研发计划(BE 2019383)

Early Detection on Wheat Canopy Powdery Mildew with Hyperspectral Imaging

CAI WeiDi(),ZHANG Yu,LIU HaiYan,ZHENG HengBiao,CHENG Tao,TIAN YongChao,ZHU Yan,CAO WeiXing,YAO Xia()   

  1. College of Agriculture, Nanjing Agricultural University/National Engineering and Technology Center for Information Agriculture/ Engineering Research Center of Smart Agriculture, Ministry of Education/Key Laboratory for Crop System Analysis and Decision Making, Ministry of Agriculture and Rural Affairs/Jiangsu Key Laboratory for Information Agriculture/Collaborative Innovation Center for Modern Crop Production Co-sponsored by Province and Ministry, Nanjing 210095
  • Received:2021-05-25 Accepted:2021-09-06 Online:2022-03-16 Published:2022-03-25
  • Contact: Xia YAO

摘要:

【目的】本研究利用近地面成像高光谱仪,获取接种白粉病菌后的小麦田间冠层时序影像,探索光谱信息与纹理信息的结合在冠层尺度上早期监测小麦白粉病的能力和表现。【方法】本试验以不同年份、不同抗病性小麦品种的田间试验为基础,利用连续小波(continuous wavelet transform,CWT)方法提取对小麦白粉病敏感的小波特征,并基于小波特征获取对应的纹理特征,用以构建归一化纹理指数(normalized difference texture index,NDTI),同时选取具有代表性的传统植被指数(vegetation indices,VIs),然后利用偏最小二乘判别分析模型(partial least squares-linear discrimination analysis,PLS-LDA)基于上述特征及组合,建立小麦冠层健康与感病状态识别模型,并利用偏最小二乘回归(partial least-squares regression,PLSR)构建了小麦冠层病情严重度估测模型,并利用该技术基于最优特征及组合判别接种后不同天数的小麦健康与感病状态。【结果】基于CWT算法入选的4个小波特征分别是6尺度的595 nm(黄光区域),5尺度的614 nm(红光区域),3尺度的708 nm(近红外区域)和4尺度的754 nm(近红外区域);进一步确定了构建最佳纹理指数组合的纹理特征有:754 nm处的熵(entropy,ENT)、均值(mean,MEA)、均一性(homogeneity,HOM),7 008 nm处的ENT、HOM,614 nm处的ENT、HOM、异质性(dissimilarity, DIS),595 nm处的ENT、HOM、DIS。其中,近红外波段754 nm处的纹理特征MEA表现最优越,与病情严重度的相关性最高(R2=0.67)。本研究进一步发现基于小波特征与纹理特征结合构建的小麦健康与病害判别PLS-LDA模型的精度最高,其总体分类精度为81.17%,Kappa系数为0.63;基于光谱指数与纹理指数组合构建的小麦病情严重度PLSR模型效果最优,建模和检验R2分别为0.76和0.71。本研究中最早能够识别的小麦冠层白粉病的病情严重度为26%左右(接种后24 d左右)。【结论】基于小波特征与纹理特征结合构建的小麦健康与病害识别模型能够显著提高病害的分类精度,而光谱指数与纹理指数的特征组合能够显著提高病情严重度的估测精度以及稳定性。本研究方法和结果可为其他作物的病害监测提供借鉴和参考,对现代智慧农业的精确施药提供了技术支持。

关键词: 小麦白粉病, 冠层, 成像高光谱, 连续小波, 纹理特征

Abstract:

【Objective】In this study, the near-ground imaging spectrometer was used to obtain time-series images of wheat canopy after inoculation with powdery mildew, which aimed to explore the ability and performance of the combination of spectral feature and texture feature in the early detection of wheat powdery mildew at canopy scale. 【Method】 Based on the field trials of wheat varieties with different disease resistance in different years, the wavelet features sensitive to wheat powdery mildew were extracted by continuous wavelet transform (CWT) method, and the corresponding texture features were extracted based on spectral features to construct normalized difference texture index (NDTI). Meanwhile, the representative traditional vegetation indices (Vis) were selected. Then, based on these features and combinations, the partial least squares discriminant analysis (PLS-LDA) model was used to establish wheat canopy healthy and disease recognition model. The partial least squares regression (PLSR) was used to estimate the severity of wheat canopy disease. The technique was used to distinguish the healthy and disease wheat at different days after inoculation based on the optimal features and combinations. 【Result】 Based on CWT, the selected four wavelet features were 595 nm (yellow region) at 6 scales, 614 nm (red region) at 5 scales, 708 nm (near infrared region) at 3 scales, and 754 nm (near infrared region) at 4 scales respectively. The following texture features were selected for the best texture index combination: ENT754, MEA754, ENT708, ENT595, ENT614, HOM708, HOM595, HOM614, DIS595, HOM754 and DIS614. Besides, it was found that the texture feature MEA754 had the superior performance among all the texture, with the highest correlation between the severity of disease and texture (R2=0.67). The PLS-LDA model based on the combination of wavelet feature and texture feature had the highest accuracy, with the overall classification accuracy of 81.17% and the Kappa coefficient of 0.63. In addition, the PLSR model based on spectral index and texture index was the best, and the R 2 of modeling and testing was 0.76 and 0.71, respectively. The severity of wheat canopy powdery mildew was about 26% (about 24 days after inoculation), which was identified in this study at the earliest time. 【Conclusion】 The wheat healthy and disease recognition model based on the combination of wavelet feature and texture feature could significantly improve the accuracy of disease classification, and the combination of spectral index and texture index could significantly improve the accuracy and stability of disease severity estimation. The method and results of this study could provide the reference for disease monitoring of other crops and technical support for accurate application of modern intelligent agriculture.

Key words: wheat powdery mildew, canopy, hyperspectral imaging, continuous wavelet transform, texture feature