Response of grapevine leaves to Plasmopara viticola infection by means of measurement of reflectance and fluorescence signals
Sebela, D., Akademie Ved, Brno (Czech Republic). Centrum Vyzkumu Globalni Zmeny | Olejnickova, J., Akademie Ved, Brno (Czech Republic). Centrum Vyzkumu Globalni Zmeny | Zupcanova, A., Jihoceska Univ., Ceske Budejovice (Czech Republic). Ustav Fyziky a Biofyziky | Sotolar, R., Mendelova Univ., Lednice (Czech Republic). Ustav Vinohradnictvi a Vinarstvi
Response of grapevine leaf tissue naturally infected by Plasmopara viticola in field was measured by means of chlorophyll fluorescence and reflectance signals. Three susceptible grapevine varieties (Cabernet Sauvignon, Pinot Blanc and Pinot Gris) were used in this study. Since the infection impairs photosynthetic activity, distribution of FV/FM parameter (maximum quantum yield of Photosystem II) over the leaf was effective to discriminate healthy and naturally infected leaf tissue. FV/FM was reduced by about 25% in all infected leaf parts. Infected leaf spots expressed significantly altered chlorophyll fluorescence induction kinetics expressing much slower electron transport rate both on donor and acceptor sites of PSII. Vegetation reflectance indices followed the variations in pigment content after the fungal infection. R750/R700 (R2 = 0.877) and CRI (carotenoid reflectance index; R2 = 0.735) were the most potent to follow changes in chlorophylls and carotenoids contents, respectively. Infected leaf tissue exhibited decrease in chlorophyll a (by about 50 %) as well as carotenoids (by about 70%). We conclude that combination of chlorophyll fluorescence and reflectance measurements can be used as an effective non-invasive tool for an early detection of Plasmopara viticola in field as well as for estimation of the level of infection.
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