Presymptomatic Detection of Powdery Mildew Infection in Winter Wheat Cultivars by Laser-Induced Fluorescence

Abstract

The sensor-based monitoring of diseases under controlled conditions establishes an objective tool that allows a better understanding of the pathogen-plant interactions in different situations. The purpose of our work was to implement the presymptomatic detection of powdery mildew on wheat leaves shortly after fungus inoculation by spectral and time-resolved laser-induced fluorescence spectroscopy. In the general scope of plant phenotyping, we hypothesized that it is possible to discriminate between wheat genotypes that are either resistant or susceptible to powdery mildew. According to our results, the presymptomatic detection of powdery mildew on wheat leaves was accomplished, irrespective of genotype, as early as one day after inoculation using the fluorescence amplitude ratio F451:F522. Similarly, the ratios F451:F522, F522:F687, and F522:F736 of the half-bandwidth are also appropriate parameters. Furthermore, in the spectral range between 410 nm and 620 nm, the mean lifetime was significantly longer in inoculated leaves than it was in control leaves. Finally, the short-term (10-12 hour) increase of the fluorescence mean lifetime at 530 nm and 560 nm following the inoculation suggests that the speed of the plant reaction might be associated to its resistance to the pathogen. Based on this information, we conclude that determinations of ultraviolet, laser-induced fluorescence intensity and lifetime are suitable approaches to presymptomatically detect powdery mildew on wheat leaves one day after inoculation.

Resveratrol stimulates phenolic metabolism and PSII efficiency in wheat infected with powdery mildew

“…For this reason, the possibility of the application of exogenous resveratrol may still be a convenient solution, especially in the so-called ecological agriculture, where use of synthetic fungicides and transgenic plants is excluded. Modern methods of early detection of powdery mildew (Bürling et al 2012) provide additional rapid identification of the disease and allow for taking countermeasures in the form of spraying.…”

Proximal Sensing of Plant-Pathogen Interactions in Spring Barley with Three Fluorescence Techniques

“…The inoculation of Blumeria graminis followed the method described in the literature [14]. Thereby, conidia of powdery mildew (Department of Phytomedicine, University of Bonn) were removed with a fine brush from infected plants and evenly distributed over the whole adaxial leaf surface of the experimental plants, particularly in a section of seven centimetres from the leaf tip.…”

“…Besides the ChlF, which is primary emitted by chlorophyll a molecules [10], several phenolic substances and other fluorophores emit a characteristically blue (F440) or green (F530) fluorescence when excited with UV radiation [11,12]. Bürling et al [9,13,14] have highlighted the potential of selected fluorescence ratios, such as the blue-to-green (F451/F522), the blue-to-red (F451/F687) and the blue-to-far-red ratio (F451/F736) for a pre-symptomatic or at least early detection of powdery mildew and leaf rust in susceptible and resistant wheat varieties. An alternative to these well-established fluorescence ratios is the determination of fluorescence lifetime [12].…”

“…An alternative to these well-established fluorescence ratios is the determination of fluorescence lifetime [12]. Modifications in the lifetime, as a result of pathogen infection, might result from the accumulation of defence-related secondary compounds leading to longer fluorescence decay [13,14]. Substances like salicylic acid and phenylpropanoid compounds were previously identified as key ones in plant disease resistance [15].…”

“…The studies done by Bürling et al [9,13,14] served as a basis for our current work targeting the potential of the imaging-based spectrally resolved fluorescence and fluorescence-indices of a portable multiparametric device to assess the impact of powdery mildew ( Blumeria graminis f. sp. hordei ) and leaf rust ( Puccinia hordei ) on the fluorescence signature of four spring barley varieties.…”