Transmission of Xylella fastidiosa Subspecies Pauca Sequence Type 53 by Different Insect Species.

Vincenzo Cavalieri,Giulio Fumarola,Michele Di Carolo,Giuseppe Altamura,Crescenza Dongiovanni,Domenico Bosco,Daniele Cornara,Maria Saponari

doi:10.3390/insects10100324

Abstract

Diseases associated with Xylella fastidiosa have been described mostly in North and South America. However, during the last five years, widespread X. fastidiosa infections have been reported in a constrained area of the Apulia region (southern Italy), in olives trees suffering a severe disease, denoted as Olive Quick Decline Syndrome (OQDS). Because many xylem sap-feeding insects can function as vectors for the transmission of this exotic pathogen in EU, several research programs are ongoing to assess the role of candidate vectors in the spread of the infections. Initial investigations identified Philaenus spumarius (L.) as the predominant vector species in the olive orchards affected by the OQDS. Additional experiments have been carried out during 2016 and 2017 to assess the role of other species. More specifically, adults of the spittlebugs Philaenus italosignus Drosopolous and Remane, Neophilaenus campestris (Fallen) and of the planthopper Latilica tunetana (Matsumura) (Issidae) have been tested in transmission experiments to assess their ability to acquire the bacterium from infected olives and to infect different susceptible hosts (olives, almond, myrtle –leaf milkwort, periwinkle). Acquisition rates determined by testing individual insects in quantitative PCR assays, ranging from 5.6% in N. campestris to 22.2% in P. italosignus, whereas no acquisition was recorded for L. tunetana. Successful transmissions were detected in the recipient plants exposed to P. italosignus and N. campestris, whereas no trasmissions occurred with L. tunetana. The known vector Philaenus spumarius has been included in all the experiments for validation. The systematic surveys conducted in 2016 and 2017 provided further evidence on the population dynamics and seasonal abundance of the spittlebug populations in the olive groves.

Highlights

Since the discovery in 2013 of the first European outbreak of the insect-transmitted bacteriumXylella fastidiosa in southern Italy (Apulia region), different strains of the bacterium have been detected in Corsica and mainland France, Balearic Islands and mainland Spain [1,2,3], and in 2018 in Portugal and in central Italy (Tuscany) [4]
The nucleotide sequences retrieved from the amplified COI genes on the DNA extracts recovered from specimens of the three spittlebugs showed high sequence identity with the sequences of the same species retrieved from the NCBI database, confirming the accurateness of the identification based on morphological characters
Accession numbers are available in NCBI GenBank under the accession numbers: MH165271 (P. spumarius), MH165272 (N. campestris) and MH165273 (P. italosignus)

Summary

Introduction

Xylella fastidiosa in southern Italy (Apulia region), different strains of the bacterium have been detected in Corsica and mainland France, Balearic Islands and mainland Spain [1,2,3], and in 2018 in Portugal and in central Italy (Tuscany) [4]. The presence of this bacterium in areas with favorable climatic conditions and the occurrence of competent insect vectors poses a serious threat to cropping systems and plants of landscape value. Confirmations that spittlebugs play an important epidemiological role in the European agro-ecosystem were obtained with the identification of Philaenus spumarius (L.) as the first ascertained European vector responsible for the severe epidemic spread of the bacterium in the olive groves in the Apulian region [14,15,16]

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