Do sharpshooters from around the world produce the same EPG waveforms? Comparison of waveform libraries from Xylella fastidiosa vectors Kolla paulula from Taiwan and Graphocephala atropunctata from California

Authors: Backus, Elaine; SHIH, HSIEN-TZUNG - Taiwan Agricultural Research Institute

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2020
Publication Date: 7/7/2020
Citation: Backus, E.A., Shih, H. 2020. Do sharpshooters from around the world produce the same EPG waveforms? Comparison of waveform libraries from Xylella fastidiosa vectors Kolla paulula from Taiwan and Graphocephala atropunctata from California. Journal of Insect Science. 20(4). Article 7. https://doi.org/10.1093/jisesa/ieaa056.
DOI: https://doi.org/10.1093/jisesa/ieaa056

Interpretive Summary: Xylella fastidiosa is a plant bacterium native to the Americas that causes lethal scorch-type diseases such as Pierce’s disease (PD) of grapevines. In 2002, a PD strain of X. fastidiosa invaded Asia for the first time, as confirmed from grape vineyards in Taiwan. Since then, X. fastidiosa has caused lossess totalling US $2.88 million. Agricultural biosecurity depends upon rapid assessment of threats from such exotic, invasive species. When the invader is a plant pathogen transmitted (carried) by an insect, feeding behavior of the vector must be studied to identify: 1) potential host plants, and 2) performance of specialized pathogen-transmitting behaviors. In Taiwan, X. fastidiosa was acquired by a native, southern Asian species of sharpshooter leafhopper, Kolla paulula, now the main vector in Taiwanese vineyards. The best tool for assessing vector feeding behavior is electropenetrography (EPG). This study used an AC-DC electropenetrograph to record feeding behaviors of K. paulula on healthy grapevines. The main objective was to identify and create a library of EPG waveforms for K. paulula. In addition, K. paulula waveforms were also compared with those from the most efficient, native vector of X. fastidiosa in California vineyards, Graphocephala atropunctata. Overall, both species of sharpshooters had similar waveform appearances, but two new waveforms were identified and a rare waveform subtype, B1p, was extensively produced in K. paulula recordings, suggesting that K. paulula could be a highly efficient X. fastidiosa vector. Thus, sharpshooter waveforms from species worldwide appear to be highly similar, and EPG methods can be rapidly applied to new species as needed.

Technical Abstract: When an exotic invasive species is a vector-borne plant pathogen, vector feeding behavior must be studied to identify potential host plant range, and its performance of specialized pathogen-transmitting behaviors. The most rigorous tool for assessing vector feeding behavior is electropenetrography (EPG). Xylella fastidiosa is a gram-negative bacterium native to the Americas, where it is the causal agent of lethal scorch-type diseases such as Pierce’s disease (PD) of grapevines. In 2002, a PD strain of X. fastidiosa invaded Asia for the first time, as confirmed from grape vineyards in Taiwan. Kolla paulula, a native, southern Asian species of sharpshooter leafhopper, was found to be the primary vector in Taiwanese vineyards. This study used an AC-DC electropenetrograph to record stylet probing behaviors of K. paulula on healthy grapevines. The main objective was to create an EPG waveform library for K. paulula. Waveform description, characterization of R versus emf components (electrical origins) and proposed biological meanings of K. paulula waveforms are reported. In addition, comparison of K. paulula waveforms with those from the most efficient, native vector of X. fastidiosa in California vineyards, Graphocephala atropunctata, is also reported. Overall, both species of sharpshooters had similar waveform appearances. Two new waveforms were identified and the previously described but rare waveform subtype, B1p, was extensively produced in K. paulula recordings. Sharpshooter waveforms from species worldwide appear to be highly similar. Thus, EPG methods can be rapidly applied to potential vectors where X. fastidiosa is newly introduced.