Abstract
Huanglongbing (HLB, citrus greening) is one of the most serious quarantine diseases of citrus worldwide. To monitor in real-time, recognize diseased trees, and efficiently prevent and control HLB disease in citrus, it is necessary to develop a rapid diagnostic method to detect HLB infected plants without symptoms. This study used Newhall navel orange plants as the research subject, and collected normal color leaf samples and chlorotic leaf samples from a healthy orchard and an HLB-infected orchard, respectively. First, hyperspectral data of the upper and lower leaf surfaces were obtained, and then the polymerase chain reaction (PCR) was used to detect the HLB bacterium in each leaf. The PCR test results showed that all samples from the healthy orchard were negative, and a portion of the samples from the infected orchard were positive. According to these results, the leaf samples from the orchards were divided into disease-free leaves and HLB-positive leaves, and the least squares support vector machine recognition model was established based on the leaf hyperspectral reflectance. The effect on the model of the spectra obtained from the upper and lower leaf surfaces was investigated and different pretreatment methods were compared and analyzed. It was observed that the HLB recognition rate values of the calibration and validation sets based on upper leaf surface spectra under 9-point smoothing pretreatment were 100% and 92.5%, respectively. The recognition rate values based on lower leaf surface spectra under the second-order derivative pretreatment were also 100% and 92.5%, respectively. Both upper and lower leaf surface spectra were available for recognition of HLB-infected leaves, and the HLB PCR-positive leaves could be distinguished from the healthy by the hyperspectral modeling analysis. The results of this study show that early and nondestructive detection of HLB-infected leaves without symptoms is possible, which provides a basis for the hyperspectral diagnosis of citrus with HLB.
Highlights
Huanglongbing (HLB, citrus greening) is a quarantinable disease of citrus around the world
The spectral reflectance of leaf samples might be influenced by many factors, such as the growth condition, leaf structure and constituents, the surrounding environment, and other factors
These factors can influence the external characteristics of leaf, such as color, texture and structure, and internal characteristics, such as chlorophyll, moisture and tissue composition, which results in some differences in spectral reflection characteristics of the leaf sample
Summary
Huanglongbing (HLB, citrus greening) is a quarantinable disease of citrus around the world. HLB has a history of more than 100 years, and is impacting the global citrus industry with increasing severity. After infection with HLB, the vigor of citrus trees gradually declines, the fruit set decreases and the production of fruits falls sharply. The fruit becomes smaller with abnormal color commonly known as “red fruit,” and lose nutritional value. When the whole plant is infected, there is almost no yield, and the tree will die[1]. There is no effective treatment for HLB disease. Real-time identification and removal of the infected plants is the most important and effective prevention and control measures
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
