UV-induced fluorescence spectra and lifetime determination for detection of leaf rust (Puccinia triticina) in susceptible and resistant wheat (Triticum aestivum) cultivars.

In modern agriculture, the use of cultivars that are resistant against specific stresses, e.g. pathogen infections, is an integral component. Considering the great demand for a rapid and objective screening method for stress resistance of new cultivars, the question arises, whether time resolved fluorescence spectroscopy is suitable for such purposes. Amongst others, infected plants might accumulate specific compounds such as salicylic acid and phenylpropanoid compounds as key substances in plant disease resistance, whereas synthesis and accumulation may influence fluorescence parameters such as absolute intensity of single peaks, ratios between peaks and lifetime. Experiments were conducted in a controlled-environment cabinet cultivating four leaf rust susceptible and three leaf rust resistant genotypes. Fluorescence measurements were conducted using a compact fibre-optic fluorescence spectrometer with a nanosecond time-resolution. Results of experiments revealed that UV-induced measurements of spectral characteristics as well as determination of fluorescence lifetime are suited to detect leaf rust (Puccinia triticina) in wheat (Triticum aestivum L.) cultivars as early as 2 days after inoculation (dai). For this purpose several parameters such as the fluorescence (F) amplitude ratios F451/F522, F451/F687, F451/F736, F522/F687, F522/F736 as well as fluorescence mean lifetime especially at 470nm, might be used. Discrimination between resistant and susceptible cultivars to the leaf rust pathogen could be accomplished 3dai by using the ratio of fluorescence amplitude between the blue (F451nm) and red (F687nm) peak, and mean lifetime at 440, 500 and 530nm. Our results indicate that the combination of spectrally and time-resolved fluorescence could be an additional tool in plant breeding programs for an automatic and precise high-throughput system for evaluation of the pathogen resistance of new genotypes.