New insights in phytoplasma‐vector interaction: acquisition and inoculation of flavescence dorée phytoplasma by Scaphoideus titanus adults in a short window of time

Abstract

The leafhopper Scaphoideus titanus is able to transmit 16SrV phytoplasmas agents of grapevine's flavescence dorée (FD) within 30–45 days, following an acquisition access period (AAP) of a few days feeding on infected plants as a nymph, a latency period (LP) of 3–5 weeks becoming meanwhile an adult, and an inoculation access period (IAP) of a few days on healthy plants. However, several aspects of FD epidemiology suggest how the whole transmission process may take less time, and may start directly with adults of the insect vector. Transmission experiments have been set up under lab condition. Phytoplasma‐free S. titanus adults were placed on broad bean (BB) plants (Vicia faba) infected by FD‐C (16SrV‐C) phytoplasmas for an AAP = 7 days. Afterwards, they were immediately moved onto healthy BB for IAP, which were changed every 7 days, obtaining three timings of inoculation: IAP 1, IAP 2 and IAP 3, lasting 7, 14 and 21 days from the end of AAP, respectively. DNA was extracted from plants and insects, and PCR tests were performed to identify FD phytoplasmas. Insects were dissected and fluorescence in situ hybridisation was made to detect the presence of phytoplasmas in midguts and salivary glands. The rate of infection in insects ranged 46–68% without significant differences among IAPs. Inoculation in plants succeeded in all IAPs, at a rate of 16–23% (no significant differences). Phytoplasma load was significantly higher in IAP 3 than IAP 1–2 for both plants and insects. Phytoplasmas were identified both in midgut and salivary glands of S. titanus at all IAP times. The possible implications of these results in the epidemiology of flavescence dorée are discussed.

Spatiotemporal dynamics and quantitative analysis of phytoplasmas in insect vectors

“…6, ii-iii). Although consideration should be given to the influence of insect stage and temperature, which can change the latency period between phytoplasma acquisition and transmission 34,35 , the infection dynamics determined in this study are consistent with those of previous studies in terms of the temporal localizations of OY and other phytoplasmas [14][15][16]24,36 and spiroplasmas 8 . Thus, the proposed model may contribute to a better understanding of the detailed dynamics of plant pathogenic bacteria in their insect vectors.…”

“…Immunohistochemical staining-based 3D imaging. At 1,2,4,6,10,14,20,27,34, and 41 daas, four leafhoppers were collected and fixed overnight in 4% paraformaldehyde. The fixed samples were dehydrated in an ethanol dilution series and embedded in Paraplast Plus (Sherwood Medical, St. Louis, MO, USA).…”

Development, Spatial Distribution, and Presence on Grapevine of Nymphs of Orientus ishidae (Hemiptera: Cicadellidae), a New Vector of Flavescence Dorée Phytoplasmas

“…ishidae acquire phytoplasmas directly on grapevine. In fact, it has recently been proved that S. titanus is capable of acquiring 16SrV phytoplasmas in the adult stage, and transmitting them within only two weeks (Alma et al 2018). Given the biological similarities between S. titanus and O. ishidae, this matter should be further investigated.…”

Temporal shifts in endophyte bacterial community composition of sessile oak (Quercus petraea) are linked to foliar nitrogen, stomatal length, and herbivory

“…As a matter of fact, herbivory could be an effective way to inoculate microbial insects symbionts, commensals and pathogens into plant tissues. It is the case, for instance, of phytoplasmas inoculated into grapevine by Hemiptera-like leafhoppers ( Gonella et al, 2008 ; Alma et al, 2018 ). In our forest plots, several herbivory traces have been recorded during the experiments.…”