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Multispectral imaging for presymptomatic analysis of light leaf spot in oilseed rape

Veys, Charles; Chatziavgerinos, Fokion; AlSuwaidi, Ali; Hibbert, James; Hansen, Mark; Bernotas, Gytis; Smith, Melvyn; Yin, Hujun; Rolfe, Stephen; Grieve, Bruce

Authors

Charles Veys

Fokion Chatziavgerinos

Ali AlSuwaidi

James Hibbert

Mark Hansen Mark.Hansen@uwe.ac.uk
Senior Research Fellow - Centre for Machine Vision

Gytis Bernotas gytis2.bernotas@live.uwe.ac.uk

Melvyn Smith Melvyn.Smith@uwe.ac.uk
Research Centre Director Vision Lab/Prof

Hujun Yin

Stephen Rolfe

Bruce Grieve



Abstract

Abstract
Background: The use of spectral imaging within the plant phenotyping and breeding community has been increasing due its utility as a non-invasive diagnostic tool. However, there is a lack of imaging systems targeted specifically at plant science duties, resulting in low precision for canopy-scale measurements. This study trials a prototype multispectral system designed specifically for plant studies and looks at its use as an early detection system for visually asymptomatic disease phases, in this case Pyrenopeziza brassica in Brassica napus. The analysis takes advantage of machine learning in the form of feature selection and novelty detection to facilitate the classification. An initial study into recording the morphology of the samples is also included to allow for further improvement to the system performance.

Results: The proposed method was able to detect light leaf spot infection with 92% accuracy when imaging
entire oilseed rape plants from above, 12 days after inoculation and 13 days before the appearance of visible
symptoms. False colour mapping of spectral vegetation indices was used to quantify disease severity and its
distribution within the plant canopy. In addition, the structure of the plant was recorded using photometric
stereo, with the output influencing regions used for diagnosis. The shape of the plants was also recorded using
photometric stereo, which allowed for reconstruction of the leaf angle and surface texture, although further
work is needed to improve the �fidelity due to uneven lighting distributions, to allow for reflectance
compensation.

Conclusions: The ability of active multispectral imaging has been demonstrated along with the improvement in time taken to detect light leaf spot at a high accuracy. The importance of capturing structural information is outlined, with its effect on reflectance and thus classification illustrated. The system could be used in plant breeding to enhance the selection of resistant cultivars, with its early and quantitative capability.

Journal Article Type Article
Publication Date Jan 1, 2019
Journal Plant Methods
Publisher BMC
Peer Reviewed Peer Reviewed
Volume 15
Issue 4
Pages 1-12
Institution Citation Veys, C., Chatziavgerinos, F., AlSuwaidi, A., Hibbert, J., Hansen, M., Bernotas, G., …Grieve, B. (2019). Multispectral imaging for presymptomatic analysis of light leaf spot in oilseed rape. Plant Methods, 15(4), 1-12. https://doi.org/10.1186/s13007-019-0389-9
DOI https://doi.org/10.1186/s13007-019-0389-9
Keywords disease detection, light leaf spot, oilseed rape, multispectral, preprocessing, machine learning, support vector machine, novelty detection, orientation effects, photometric stereo
Publisher URL https://doi.org/10.1186/s13007-019-0389-9

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