Effects of grape downy mildew on photosynthesis of 'Niagara' grapevine leaves

Downy mildew (Plasmopara viticola) reduces photosynthesis in infected leaf areas of grapevines. To study the underlying physiological causes, leaves of potted 'Niagara' vines were artificially inoculated with sporangia of P. viticola. Photosynthesis and chlorophyll fluorescence in the inoc...

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Bibliographic Details
Published in:Phytopathology 2005-06, Vol.95 (6), p.S170-S170
Main Authors: Lehman, B L, Flore, JA, Schilder, AMC
Format: Article
Language:English
Subjects:
Plasmopara viticola
Vitaceae
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Summary:Downy mildew (Plasmopara viticola) reduces photosynthesis in infected leaf areas of grapevines. To study the underlying physiological causes, leaves of potted 'Niagara' vines were artificially inoculated with sporangia of P. viticola. Photosynthesis and chlorophyll fluorescence in the inoculated area were measured at 48-h intervals after inoculation, while an uninoculated area on each leaf served as a control. Symptoms appeared 7 days after inoculation but physiological changes occurred before that. Chlorophyll fluorescence, a negative indicator of Photosystem II efficiency, increased while carboxylation efficiency, quantum efficiency, maximum photosynthesis, stomatal conductance, carbon dioxide compensation point, and light compensation point decreased significantly compared to the control. Carboxylation efficiency decreased earlier and more rapidly than the other parameters, indicating a decrease in ribulose-1,5-bisphosphate (RuBP) concentration or RuBP carboxylase (Rubisco) activity.
ISSN:0031-949X
DOI:10.1094/PHYTO.2005.95.6.S168