In recent years, natural compounds have gained attention in many fields due to their wide-range biological activity. In particular, essential oils and their associated hydrosols are being screened to control plant pests, exerting antiviral, antimycotic and antiparasitic actions. They are more quickly and cheaply produced and are generally considered safer for the environment and non-target organisms than conventional pesticides. In this study, we report the evaluation of the biological activity of two essential oils and their corresponding hydrosols obtained from Mentha suaveolens and Foeniculum vulgare in the control of zucchini yellow mosaic virus and its vector, Aphis gossypii, in Cucurbita pepo plants. The control of the virus was ascertained with treatments applied either concurrently with or after virus infection; choice tests were performed to verify repellency activity against the aphid vector. The results indicated that treatments could decrease virus titer as measured using real-time RT-PCR, while the experiments on the vector showed that the compounds effectively repelled aphids. The extracts were also chemically characterized using gas chromatography–mass spectrometry. Mentha suaveolens and Foeniculum vulgare hydrosol extracts mainly comprised fenchone and decanenitrile, respectively, while essential oils analysis returned a more complex composition, as expected.

Hop (Humulus lupulus L.) is a minor ingredient in the beer production but has a strong influence on the beer quality due to the high chemical complexity of the cones used in brewing. One of the major factors that can severely affect the chemical composition of the hop cones and their marketability is the presence of viral infections in the plant. Amongst the five major hop viruses, three belong to the Carlavirus genus: hop mosaic virus (HpMV), hop latent virus (HpLV), and American hop latent virus (AHLV). The occurrence of carlaviruses on hop germplasm in Italy was firstly recorded in 2017 but, in that context, a generic detection was only performed and no information on the infecting Carlavirus species was provided. To fill this gap, 51 hop samples previously found infected by carlaviruses were analysed by RT-PCR employing primer pairs specific for the coat protein (CP) of HpMV, HpLV and AHLV, respectively. HpLV resulted largely prevalent as it was detected in 96.1% of tested samples whereas for HpMV and AHLV an infection rate of 5.9% and 3.9% was recorded, respectively. CP nucleotide sequences from 13 selected virus isolates were obtained and analysed; moreover, the complete genome sequence of 7 isolates was obtained by using high throughput sequencing (HTS). Phylogenetic analysis showed close relationships among isolates from different geographical origin, including European and non-European countries, according to the worldwide movement of hop germplasm due to global trade. This is the first report of HpMV, HpLV and AHLV on hop germplasm in Italy.

The use of organic substances in integrated pest management can contribute to human- and environment-safe crop production. In the present work, a combination of organic biostimulants (Fullcrhum Alert and BioVeg 500) and an inorganic corroborant (Clinogold, zeolite) was tested for the effects on the plant response to the quarantine pest tomato leaf curl New Delhi virus (ToLCNDV). Biostimulants were applied to healthy and infected greenhouse-grown zucchini plants, and the vegetative parameters and viral titer were evaluated. Although no antiviral effects were observed in terms of both virus replication and symptom expression, these biostimulants were shown to influence plant fitness. A significant increase in biomass and in leaf, flower, and fruit production was induced in both healthy and infected plants. Biostimulants also enhanced the production of metabolites commonly involved in plant response to virus infection, such as carbohydrates, phenylpropanoids and free amino acids. These results encourage new field trials to evaluate the actual productivity of infected plants after treatments and the possible application of organic biostimulants in agriculture.

In agriculture, new and sustainable strategies are increasingly demanded to integrate the traditional management of viral diseases based on the use of virus-free propagation materials and resistant or tolerant cultivars and on the control of insect vectors. Among the possible Integrated Pest Management (IPM) approaches, organic biostimulants have shown promising results in enhancing plant tolerance to virus infections by improving plant fitness and productivity and modulating metabolic functions. In this study, the combination of two organic biostimulants, Alert D-Max and Resil EVO Q, composed of seaweed and alfalfa extracts, enzymatic hydrolysates, and micronized zeolite, was applied on the leaves and roots of zucchini squashes, both healthy and infected by zucchini yellow mosaic virus (ZYMV). Four applications were scheduled based on ZYMV inoculation timing, and plant vegetative and reproductive parameters were recorded along with the virus titre and symptom severity. The modulation of the expression of specific genes potentially involved in pattern-triggered immunity (PTI), systemic acquired resistance (SAR), and oxidative stress defence pathways was also investigated. Besides increasing the general fitness of the healthy plants, the biostimulants significantly improved the production of flowers and fruits of the infected plants, with a potential positive impact on their productivity. The repeated biostimulant applications also led to a one-tenth reduction in ZYMV titre over time and induced a progressive slowdown of symptom severity. Genes associated with SAR and PTI were up-regulated after biostimulant applications, suggesting the biostimulant-based priming of plant defence mechanisms. Due to the observed beneficial effects, the tested biostimulant mix can be an effective component of the IPM of cucurbit crops, acting as a sustainable practice for enhancing plant fitness and tolerance to potyviruses.

Italy is the second largest producer of hazelnuts in the world after Turkey. The Viterbo province (Latium region) is one out of the four main productive districts, accounting for approximately 30% of the total Italian production. Several pathogens can severely affect hazelnut trees (Corylus avellana), mainly fungi and bacteria that are commonly spread in all the growing areas. However, other pathogens such as phytoplasmas, are known to infect this crop worldwide. Among these, ‘Candidatus Phytoplasma fragariae’ (16SrXII-E) has been recently associated with the decline and death of hazelnut trees in UK where it was identified for the first time on this plant species (Hodgetts et al., 2015), and in Slovenia (Mehle et al., 2018; Mehle et al., 2019). In July 2020, a survey was carried out in two orchards located in the Viterbo province, where symptoms resembling those induced by phytoplasmas and consisting in yellowing and rolling of leaves and tree decline (Supplementary figure 1) were recorded by growers. To ascertain the possible presence of phytoplasma infections, leaf samples were collected from five symptomatic plants: one plant from orchard 1, cv. Tonda Gentile Romana and four plants from orchard 2, cv. Tonda di Giffoni. Samples from four non-symptomatic plants (two per each orchard) were also collected and used as negative controls in the detection assays. DNA was extracted from 0.6 g of leaf ribs homogenised in CTAB buffer according to Marzachì et al. (1999). DNA extracts were amplified by direct and nested PCR employing the universal primer pairs P1/P7 and R16F2n/R2 according to the EPPO Standard PM7/133(1) - Appendix 2 (EPPO, 2018). Nested amplicons of the expected size (1,250 bp) were obtained from the five symptomatic samples whereas no bands were observed for the symptomless ones. The R16F2n/R2 fragments were submitted to both Sanger sequencing and RFLP analysis for the phytoplasma identification. Nucleotide BLAST analysis (NCBI) of the obtained sequences showed an identity percentage ranging from 99.65% and 99.91% with numerous strains of ‘Ca. Phytoplasma fragariae’ (16SrXII-E). The RFLP analysis was performed with the MseI restriction enzyme, and the obtained profiles were compared in the Codon Code Aligner software to those virtually generated from reference sequences of phytoplasmas belonging to the 16SrXII subgroups identified so far (Kazeem et al., 2021). All the five samples showed a common RFLP profile which was ascribable to that virtually generated from the 16SrXII-E reference sequence DQ086423 (Valiunas et al., 2006) (Supplementary figure 2). To our knowledge, this is the first finding of ‘Ca. P. fragariae' on hazelnut in Italy since the previous records on woody plant hosts regarded Cornus sanguinea and Sambucus nigra (Filippin et al. 2008). Further surveys are ongoing to assess the spread of ‘Ca. P. fragariae' in the Italian hazelnut orchards and to identify the putative insect vectors. The nucleotide sequences obtained in this study were deposited in GenBank NCBI database (accession numbers: MW767127, MW767128, MW767129, MW767130, MW767131).