Xylella fastidiosa subspecies and sequence types detected inPhilaenus spumarius and in infected plants in France share the same locations
In Europe, the meadow spittlebugPhilaenus spumariusis the main known vector of the quarantine bacteriumXylella fastidiosa. So far detection and identification ofX.fastidiosahas more often been performed from plant matrices than insects, mainly using a real-time PCR and multilocus sequence typing (MLST) approach. Detection ofX.fastidiosain its insect vectors would enhance knowledge of the epidemiologic situation in France, specifically in the already infected Corsica and Provence-Alpes-Cote d'Azur (PACA) regions. The aim of this study was to validate a methodological approach to detectX.fastidiosainP.spumarius, analysed individually or in groups of 10, using real-time PCR and MLST, and to apply the approach to more than 4,000 individuals collected between 2015 and 2019 from infected areas. The corresponding results expanded our knowledge of the epidemiology ofX.fastidiosain France: (a)X.fastidiosasubsp.multiplexincluding the sequence types ST6 and ST7 were identified in the insect vector; (b) the rate of positive insects per infected area was as high as 33.3% in Corsica or 50% in the PACA region; (c) positive adults were found during winter; and (d) the bacterial load inP.spumarius(droplet digital PCR) usually ranged from 10(3)to 10(4)cells per insect, but could be as high as 10(5)or 10(6)cells per insect for some individuals (13%). The subspecies and sequence types detected inP.spumariuscorresponded to the situation officially reported for plants in the same areas.