|SHIH, HSIEN-TZUNG - Taiwan Agricultural Research Institute|
Submitted to: Journal of Insect Science
Publication Type: Review Article
Publication Acceptance Date: 5/18/2020
Publication Date: 7/7/2020
Citation: Backus, E.A., Shih, H. 2020. Review of the EPG waveforms of sharpshooters and spittlebugs including their biological meanings in relation to transmission of Xylella fastidiosa (Xanthomonadales: Xanthomonadaceae). Journal of Insect Science. 20(4):6;1-14. https://doi.org/10.1093/jisesa/ieaa055.
Technical Abstract: Electropenetrography (EPG) is one of the most rigorous methods to study stylet probing behaviors of piercing-sucking insects whose mouthparts move invisibly inside hosts. EPG is particularly useful for identifying: 1) vector behaviors that control transmission (acquistion and inoculation) of plant pathogens, 2) comparing those behaviors among vector species, and 3) aiding in development of novel vector and disease management tactics. Xylella fastidiosa is a gram-negative, invasive bacterium native to the Americas, where it is the causal agent of lethal scorch-type diseases such as Pierce’s disease (PD) of grapevines. X. fastidiosa is transmitted by sharpshooter leafhoppers (Cicadellidae: Cicadellinae) and spittlebugs (Aphrophoridae). Despite over 75 years of study, details of the inoculation mechanism of X. fastidiosa were unknown until the advent of EPG research with sharpshooters. Herein, the following topics are presented: 1) review of key EPG principles and waveforms published to date, emphasizing sharpshooters and spittlebugs; 2) summarize the present understanding of biological meanings of sharpshooter waveforms; 3) review mechanisms of transmission for X. fastidiosa illuminated by EPG; and 4) recommend the most useful waveform categories for use in future, quantitative comparisons of sharpshooter stylet probing on various treatments such as infected versus uninfected plants, or resistant varieties. In addition, new work on the functional anatomy of the precibarial valve is discussed in the context of X. fastidiosa transmission mechanisms and EPG waveform meanings. Also, the first block diagram of secondary, signal-processing circuitry for the AC-DC electropenetrograph is published, and is discussed in relation to EPG signals appearances and meanings.