Potential of fungi of the genus Trichoderma for biocontrol of Philaenus spumarius, the insect vector for the quarantine bacterium Xylella fastidosa.

BACKGROUND: The meadow spittlebug Philaenus spumarius L. is the vector for the bacterium Xylella fastidiosa subspecies pauca, involved in olive quick decline syndrome (OQDS) in Salento (Italy). Control of P. spumarius is key to limiting transmission of the bacterium, and an innovative approach can be based on effective natural compounds and biocontrol agents. Entomopathogenic fungi are an important source of bioactive natural molecules that play a role in the relationship between microorganisms and insects. RESULTS: Pathogenicity bioassays, performed by dipping adults of P. spumarius in either fungal culture suspension (120 mg mL-1 ) or cell-free culture supernatant of Trichoderma chlorosporum GJS 91-150, showed, respectively, 97% and 87% death within 24 h. The effect was dose-dependent. In laboratory bioassays, the powdered fungal culture of T. chlorosporum GJS 91-150 did not exhibit pathogenic activity when injected into nymph spittle. CONCLUSIONS: T. chlorosporum GJS 91-150 affected the survival of P. spumarius adults. The lethal effect was not associated with the development of mycelium on the cuticle, but seems due, at least partly, to fungal metabolites released in the culture medium. The fungus tested here has good potential for the development of effective low-environmental impact control strategies for P. spumarius and suppression of X. fastidiosa. © 2022 Society of Chemical Industry.

SARS-CoV-2 Subgenomic N (sgN) Transcripts in Oro-Nasopharyngeal Swabs Correlate with the Highest Viral Load, as Evaluated by Five Different Molecular Methods.

The COVID-19 pandemic has forced diagnostic laboratories to focus on the early diagnostics of SARS-CoV-2. The positivity of a molecular test cannot respond to the question regarding the viral capability to replicate, spread, and give different clinical effects. Despite the fact that some targets are covered by commercially-available assays, the identification of new biomarkers is desired in order to improve the quality of the information given by these assays. Therefore, since the subgenomic transcripts (sgN and sgE) are considered markers of viral activity, we evaluated these subgenomic transcripts in relation to the genomic amplification obtained using five different commercial CE-IVD tools. Methods: Five CE-IVD kits were compared in terms of their capability to detect both synthetic SARS-CoV-2 viral constructs (spiked in TMB or PBS medium) and targets (N, E, RdRp and Orf1ab genes) in twenty COVID-19-positive patients' swabs. The sgN and sgE were assayed by real-time RT-qPCR and digital PCR. Results: None of the diagnostic kits missed the viral target genes when they were applied to targets spiked in TMB or PBS (at dilutions ranging from 100 pg to 0.1 pg). Nevertheless, once they were applied to RNA extracted from the patients' swabs, the superimposability ranged from 50% to 100%, regardless of the extraction procedure. The sgN RNA transcript was detected only in samples with a higher viral load (Ct ≤ 22.5), while sgE was within all of the Ct ranges. Conclusions: The five kits show variable performances depending on the assay layout. It is worthy of note that the detection of the sgN transcript is associated with a higher viral load, thus representing a new marker of early and more severe infection.

Electrophysiological and behavioural response of Philaenus spumarius to essential oils and aromatic plants.

The meadow spittlebug, Philaenus spumarius, is a highly polyphagous widespread species, playing a major role in the transmission of the bacterium Xylella fastidiosa subspecies pauca, the agent of the "Olive Quick Decline Syndrome". Essential oils (EOs) are an important source of bio-active volatile compounds that could interfere with basic metabolic, biochemical, physiological, and behavioural functions of insects. Here, we report the electrophysiological and behavioural responses of adult P. spumarius towards some EOs and related plants. Electroantennographic tests demonstrated that the peripheral olfactory system of P. spumarius females and males perceives volatile organic compounds present in the EOs of Pelargonium graveolens, Cymbopogon nardus and Lavandula officinalis in a dose-dependent manner. In behavioral bioassays, evaluating the adult responses towards EOs and related plants, both at close (Y-tube) and long range (wind tunnel), males and females responded differently to the same odorant. Using EOs, a clear attraction was noted only for males towards lavender EO. Conversely, plants elicited responses that varied upon the plant species, testing device and adult sex. Both lavender and geranium repelled females at any distance range. On the contrary, males were attracted by geranium and repelled by citronella. Finally, at close distance, lavender and citronella were repellent for females and males, respectively. Our results contribute to the development of innovative tools and approaches, alternative to the use of synthetic pesticides, for the sustainable control of P. spumarius aiming to contrasting the expansion of X. fastidiosa.