Thermal and Chlorophyll-Fluorescence Imaging Distinguish Plant-Pathogen Interactions at an Early Stage

TLDR

Different biotic stresses produce specific symptoms due to distinct physiological effects, and identifying disease signatures for various plant‑pathogen interactions could enable early detection of biotic stresses in crops, facilitating outbreak containment. The study aimed to monitor early changes in a plant’s physiological status upon pathogen attack by simultaneously applying chlorophyll‑fluorescence imaging and thermography to two fundamentally different plant‑pathogen interactions. Under growth‑room conditions, a robotized set‑up captured time‑series of visual, thermal and chlorophyll‑fluorescence images from infected leaf regions while chlorophyll‑fluorescence imaging and thermography were performed in parallel to monitor photosynthetic efficiency and transpiration. The non‑destructive imaging techniques detected early infection signatures, with thermal imaging showing a local temperature rise and increased fluorescence in tobacco–TMV interaction, while in sugar beet–Cercospora beticola the opposite pattern of lower temperature and higher fluorescence spots was observed, demonstrating that presymptomatic monitoring can.

Abstract

Different biotic stresses yield specific symptoms, owing to their distinct influence on a plant's physiological status. To monitor early changes in a plant's physiological status upon pathogen attack, chlorophyll fluorescence imaging (Chl-FI) and thermography, which respectively visualize photosynthetic efficiency and transpiration, were carried out in parallel for two fundamentally different plant-pathogen interactions. These non-destructive imaging techniques were able to visualize infections at an early stage, before damage appeared. Under growth-room conditions, a robotized set-up captured time series of visual, thermal and chlorophyll fluorescence images from infected regions on attached leaves. As a first symptom of the plant-virus interaction between resistant tobacco and tobacco mosaic virus (TMV), thermal imaging detected a local rise in temperature while Chl-FI monitored a co-localized increase in fluorescence intensity. Chl-FI also revealed pre-symptomatic high-intensity spots for the plant-fungus system sugar beet-Cercospora beticola. Concomitantly, spots of lower temperature were monitored with thermography, in marked contrast with our observations on TMV-infection in tobacco. Knowledge of disease signatures for different plant-pathogen interactions could allow early identification of emerging biotic stresses in crops, facilitating the containment of disease outbreaks. Presymptomatic monitoring clearly opens perspectives for quantitative screening for disease resistance, either on excised leaf pieces or attached leaves.