Autofluorescence of grape berries following Botrytis cinerea infection

Abstract

Grey mould is caused by Botrytis cinerea, a fungus infecting over 200 plant species worldwide and causing tremendous harvest losses in vineyards. We evaluated the potential of plant fluorescence to achieve early detection of B. cinerea in grapevine (Vitis vinifera L.) berries. By comparing control and artificially inoculated berries, six images of fluorescence were taken at four wavelengths under 360 nm excitation (F ₄₄₀/F₃₆₀ (fluorescence emitted at 440 nm under a 360 nm excitation), F ₅₂₀/F₃₆₀, F ₆₉₀/F₃₆₀ and F ₇₉₀/F₃₆₀) and at two wavelengths under 436 nm excitation (F ₆₉₀/F₄₃₆ and F ₇₉₀/F₄₃₆). Data treatments include proper image correction, interest area selection, fluorescence ratios computation and edge detection. In the early stages, before 3 DAI (days after inoculation), the discrimination between wounded and symptomatic berries could not easily be achieved using blue fluorescence solely (440 nm). However, using blue out of far-red fluorescence ratio (F ₄₄₀/F ₇₄₀), it was possible to detect infected berries starting as early as 4 DAI. Using image analysis and edge detection over UV-epidermal transmittance measured at 690 nm, it was possible to detect botrytized berries as early as 3 DAI.

Acknowledgements

The authors wish to thank Dr Alain A. Viau from the Agricultural and Applied Geomatic (GAAP) laboratory in Québec, Canada, for the access to fluorescence instruments and J. ROUDET (UMR, Santé végétale, Bordeaux) for technical assistance.