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United States Department of Agriculture

Agricultural Research Service

Research Project: Epidemiology and Management of Pierce's Disease and Other Maladies of Grape

Location: Crop Diseases, Pests and Genetics

Title: Effects of plant water stress on vector feeding behaviors that control acquisition and inoculation of Xylella fastidiosa

Authors
item Backus, Elaine
item Krugner, Rodrigo

Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: November 3, 2012
Publication Date: February 21, 2013
Citation: Backus, E.A., Krugner, R. 2013. Effects of plant water stress on vector feeding behaviors that control acquisition and inoculation of Xylella fastidiosa. p. 1.In: 2012 Pierce's Disease Research Progress Reports, California Department of Food and Agriculture, 262 pp.

Interpretive Summary: Xylella fastidiosa (Xf) is an economically important bacterial pathogen of grapevines (Pierce’s disease), almond, nursery trees, and ornamental plants in California. The bacterium is transmitted from plant to plant by sharpshooter leafhopper vectors, such as the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis. Vector feeding behavior directly controls Xf acquisition and inoculation. The present study tested whether plant water stress affects vector performance of acquisition and/or inoculation behaviors. GWSS feeding behaviors on well-watered vs. water-stressed plants (almond vs. Navel orange) were recorded using electrical penetration graph (EPG). EPG waveforms representing searching for xylem, xylem contact, and ingestion of xylem sap were analyzed. Results showed that duration of xylem-sap ingestion per insect (controlling acquisition) was shorter on water-stressed than on well-watered plants. Number of xylem contacts per insect (likely to control inoculation) also were lower when plants were watered-stressed. Thus, both acquisition and inoculation behaviors were decreased on water-stressed plants. These findings support other studies suggesting that reduced irrigation may impact Pierce’s disease spread by reducing bacterial acquisition and/or inoculation by the vector.

Technical Abstract: Feeding behavior by vectors of Xylella fastidiosa (Xf) such as the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, directly controls Xf transmission (especially acquisition and inoculation). The present study tested whether plant water stress affects vector performance of acquisition and/or inoculation behaviors. GWSS feeding behaviors on well-watered vs. water-stressed plants were recorded using electrical penetration graph (EPG); plants studied were almond (Prunus dulcis cv ‘Sonora’) and Navel orange (Citrus sinensis cv ‘Navel’). EPG waveforms likely to control Xf inoculation and acquisition were analyzed. Waveforms included pathway phase (searching for xylem), X waves (xylem contact, likely to control inoculation), and waveform C2 (ingestion of xylem fluid, controlling acquisition) were analyzed. Results showed that duration of xylem-sap ingestion per insect was shorter on water-stressed than on well-watered plants. Number of xylem contacts per insect also was lower when plants were watered-stressed. Thus, both acquisition and inoculation behaviors were decreased on water-stressed plants. These findings support other studies suggesting that diminished irrigation may impact Pierce’s disease epidemiology by reducing bacterial acquisition and/or inoculation by the vector.

Last Modified: 11/22/2014
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