EPG combined with micro-CT and video recording reveals new insights on the feeding behavior of Philaenus spumarius.

Daniele Cornara,Elisa Garzo,Aranzazu Moreno,Marina Morente,Alberto Fereres,Javier Alba-Tercedor,Arash Rashed

doi:10.1371/journal.pone.0199154

Daniele Cornara, Elisa Garzo + Show 5 more

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https://doi.org/10.1371/journal.pone.0199154

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Abstract

The meadow spittlebug Philaenus spumarius plays a key role in the transmission of the bacterium Xylella fastidiosa to olive in Apulia (South Italy). Currently, available data on P. spumarius feeding behavior is limited, and a real-time observation of the different steps involved in stylet insertion, exploratory probes, and ingestion, has never been carried out. Therefore, we performed an EPG-assisted characterization of P. spumarius female feeding behavior on olive, in order to detect and analyze the main EPG waveforms describing their amplitude, frequency, voltage level, and electrical origin of the traces during stylet penetration in plant tissues. Thereafter, each of the main waveforms was correlated with specific biological activities, through video recording and analysis of excretion by adults and excretion/secretion by nymphs. Furthermore, the specific stylet tips position within the plant tissues during each of the waveforms observed was assessed by microcomputer tomography (micro-CT). Additional EPG-recordings were carried out with males of P. spumarius on olive, in order to assess possible sex-related differences. P. spumarius feeding behavior can be described by five main distinct waveforms: C (pathway), Xc (xylem contact/pre-ingestion), Xi (xylem sap ingestion), R (resting), N (interruption within xylem phase). Compared to males, females require shorter time to begin the first probe, and their Xi phase is significantly longer. Furthermore, considering the single waveform events, males on olive exhibit longer np and R compared to females.

Highlights

One of the primary concerns of the global fruit industry is a group of systemic plant pathogens, i.e. virus, viroids, phytoplasmas and bacteria, for which there are not remedies once the plant is infected
For P. spumarius, five main waveforms were identified and named following almost the same terminology as Miranda et al [44], according to their high similarity with the ones reported for Bucephalogonia xanthophis Berg (1879) (Hemiptera: Cicadellidae): C, Xc, xylem ingestion (Xi), R and N (Fig 3)
Waveform C stands for pathway, including both stylet penetration and withdrawal; Xc and Xi represent xylem contact/pre-ingestion and active xylem ingestion, respectively; R indicates resting occurring during xylem activity; N represents an interruption during xylem phase

Summary

Introduction

One of the primary concerns of the global fruit industry is a group of systemic plant pathogens, i.e. virus, viroids, phytoplasmas and bacteria, for which there are not remedies once the plant is infected. The spread of these pathogens after the introduction into a new location generally relies on native or introduced vectors [1, 2, 3, 4]. Activity, and behavior, are key factors for the transmission of insect-borne plant pathogens [5]. Philaenus spumarius feeding behavior and analysis, decision to publish, or preparation of the manuscript. For the micro-CT, the work benefited of the project: “Developing an Infrastructure and Product Test Pipeline to Deliver Novel Therapies for Citrus Greening Disease”, USDA NIFA Award No.2015-70016-23028

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