Salicaceae as potential host plants ofXylella fastidiosain European temperate regions

Abstract

The discovery of three subspecies of Xylella fastidiosa in Europe has triggered major attention on the potential spread up North of the bacteria. Assessing the susceptibility of a previously unexposed European flora is a key element that remains widely unknown. Under biosafety facility, we evaluated the susceptibility of Salicaceae such as Populus tremula, Populus canescens, Salix alba and Salix caprea by mechanically inoculating the KLN59.3 GFP-labelled X. fastidiosa at 22 C and at 28 C. Bacterial movement and multiplication in plants were investigated by PCR, real-time PCR, confocal or scanning electron microscopy. Nine months post-inoculation, 100 % of the plants tested positive for X. fastidiosa, with the exception of 57% for P. canescens under the 22 C-growing conditions. Bacteria were detected up to 120 cm from the inoculation point for S. alba. They were detected in the roots of all species and were successfully isolated for S. alba and P. tremula. Estimates of average CFU/g of plant tissue per species ranged from 1.5E + 03 to 3.5E + 06, with the lowest figures for P. canescens and the highest for P. tremula together with high number of totally obstructed vessels observed by confocal microscopy. The possibility of insect transmission was also evaluated using an experimental set up based on Mallorca Island. There, transmission by P. spumarius of both X. fastidiosa ST1 and ST81 was proven on S. alba. We thus demonstrated that indigenous European Salicaceae such as S. alba or P. tremula are new potential hosts for X. fastidiosa.

Insect-habitat-plant interaction networks provide guidelines to mitigate the risk of transmission of Xylella fastidiosa to grapevine in Southern France

“…and A. grp. salicina were specialists, each thriving on almost only one plant family, confirming the biological informations available for these species (Casarin et al, 2021;Morente et al, 2018).…”

“…As a consequence, greater damage due to Pierce's disease was observed near rivers (Purcell, 2013). In Belgium, Casarin et al (2021) suggested that Salicaceae, abundant on river banks, hosted populations of vectors of Xf (especially Aphrophora grp. salicina).…”

“…in meadows, or Cicadella viridis and Aphrophora spp. in riparian habitats (Casarin et al, 2021;Morente et al, 2018;Thompson et al, 2023); 2/ the biggest reservoirs would be mainly semi-natural herbaceous strata (meadow, alfalfa, riparian vegetation) (Casarin et al, 2021;Weaver & King, 1954).…”