Pre-symptomatic detection of Plasmopara viticola infection in grapevine leaves using chlorophyll fluorescence imaging

Abstract

Plasmopara viticola is an economically important pathogen of grapevine. Early detection of P. viticola infection can lead to improved fungicide treatment. Our study aimed to determine whether chlorophyll fluorescence (Chl-F) imaging can be used to reveal early stages of P. viticola infection under conditions similar to those occurring in commercial vineyards. Maximum (F(V)/F(M)) and effective quantum yield of photosystem II (I broken vertical bar(PSII)) were identified as the most sensitive reporters of the infection. Heterogeneous distribution of F(V)/F(M) and I broken vertical bar(PSII) in artificially inoculated leaves was associated with the presence of the developing mycelium 3 days before the occurrence of visible symptoms and 5 days before the release of spores. Significant changes of F(V)/F(M) and I broken vertical bar(PSII) were spatially coincident with localised spots of inoculation across the leaf lamina. Reduction of F(V)/F(M) was restricted to the leaf area that later yielded sporulation, while the area with significantly lower I broken vertical bar(PSII) was larger and probably reflected the leaf parts in which photosynthesis was impaired. Our results indicate that Chl-F can be used for the early detection of P. viticola infection. Because P. viticola does not expand systemically in the host tissues and the effects of infection are localised, Chl-F imaging at high resolution is necessary to reveal the disease in the field

Defence responses in Rpv3-dependent resistance to grapevine downy mildew

“…Furthermore, a variable proportion of attempted infections also abort in susceptible hosts, and the hyphae that successfully establish biotrophy in a substomatal cavity expand only within the surrounding polygonal sector of the mesophyll, with their peripheral boundaries demarcated by vascular tissues. As a result, the colonised/sporulating area is delimited within variable portions of the leaf lamina even in the event of susceptibility (Unger et al 2007;Cséfalvay et al 2009). All in all, localised responses in resistant individuals, patchy distribution of the infection in susceptible individuals and variable disease sensitivity among leaves and plants of the same host genotype are major factors that increase the experimental error of quantitative readings.…”

Evaluation of “ground sensing” optical sensors for diagnosis of Plasmopara viticola on vines

“…Delalieux et al (2007) investigated the capability of hyperspectral analysis for early white apple scab (Venturia inaequalis) detection and to develop an approach to explore this potential. Cséfalvay et al (2009) conducted a study on the pre-symptomatic detection of Plasmopara viticola (Berk. et Curt.…”

Recent advances in sensing plant diseases for precision crop protection

“…These methods may be very sensitive in the detection of abnormalities in photosynthesis-see e.g. reviews byScholes and Rolfe (2009) andChaerle et al (2009) as well asCsefalvay et al (2009)-the use of these active sensors in the field, however, is also limited by the response time, i.e. the time between emission and detection of the measuring beam, restricting the use for on-the-move sensing.…”