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United States Department of Agriculture

Agricultural Research Service

Title: Correlation of Stylet Activities by the Glassy-Winged Sharpshooter, Homalodisca Coagulata (Say), with Electrical Penetration Graph (Epg) Waveforms

Authors
item Joost, P - UNIV OF CALIF-RIVERSIDE
item Backus, Elaine
item Yan, Fengming - PEKING UNIVERSITY-CHINA

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2005
Publication Date: March 1, 2006
Citation: Joost, P.H., Backus, E.A., Yan, F. 2006. Correlation of stylet activities by the glassy-winged sharpshooter, Homalodisca coagulata (Say), with electrical penetration graph (EPG) waveforms. Journal of Insect Physiology. 52(3):327-337

Interpretive Summary: Glassy-winged sharpshooer (GWSS), Homalodisca coagulata (Say), is an efficient vector of Xylella fastidiosa (Xf), the causal bacterium of Pierce’s disease, and leaf scorch in almond and oleander. Acquisition and inoculation of Xf occur sometime during the process of stylet penetration into the plant. That process is most rigorously studied via electrical penetration graph (EPG) monitoring of insect feeding. This study provides part of the crucial biological meanings that define the waveforms of each new insect species recorded by EPG. By synchronizing AC EPG waveforms with high-magnification video of GWSS stylet penetration in artifical diet, we correlated GWSS stylet activities with three previously described EPG pathway waveforms, A1, B1 and B2, as well as one ingestion waveform, C. This detailed understanding of stylet penetration behaviors of GWSS is an important step toward identifying the instant of bacterial inoculation which, in turn, will be applied to studies of disease epidemiology and development of host plant resistance.

Technical Abstract: Glassy-winged sharpshooer (GWSS), Homalodisca coagulata (Say), is an efficient vector of Xylella fastidiosa (Xf), the causal bacterium of Pierce’s disease, and leaf scorch in almond and oleander. Acquisition and inoculation of Xf occur sometime during the process of stylet penetration into the plant. That process is most rigorously studied via electrical penetration graph (EPG) monitoring of insect feeding. This study provides part of the crucial biological meanings that define the waveforms of each new insect species recorded by EPG. By synchronizing AC EPG waveforms with high-magnification video of GWSS stylet penetration in artifical diet, we correlated GWSS stylet activities with three previously described EPG pathway waveforms, A1, B1 and B2, as well as one ingestion waveform, C. Waveform A1 occured at the beginning of stylet penetration. Subtypes of this waveform were correlated with salivary sheath trunk formation, repetitive stylet movements involving retraction of both maxillary stylets and one mandibular stylet, extension of the stylet fascicle, and the fluttering-like movements of the maxillary stylet tips. Waveform B1 was ubitquious, interspersed throughout the other waveforms. B1 subtype, B1w, was correlated with salivation followed by maxillary tip fluttering. This tip fluttering occurred before and during B1 subtype B1s, but was not directly correlated with either the occurrence or frequency of this waveform. Waveform B2 was correlated with sawing-like maxillary stylet movements, which caused salivary sheath branching. Waveform C was correlated with ingestion. Fluid outflow was also observed as a mechanism to clear the maxillary tips from debris during waveform C. This detailed understanding of stylet penetration behaviors of GWSS is an important step toward identifying the instant of bacterial inoculation which, in turn, will be applied to studies of disease epidemiology and development of host plant resistance.

Last Modified: 8/30/2014
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