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Olive quick decline syndrome (OQDS) is a disease that has been seriously affecting olive trees in southern Italy since around 2009. During the disease, caused by Xylella fastidiosa subsp. pauca sequence type ST53 (Xf), the flow of water and nutrients within the trees is significantly compromised. Initially, infected trees may not show any symptoms, making early detection challenging. In this study, young artificially infected plants of the susceptible cultivar Cellina di Nardò were grown in a controlled environment and co-inoculated with additional xylem-inhabiting fungi. Asymptomatic leaves of olive plants at an early stage of infection were collected and analyzed using nuclear magnetic resonance (NMR), hyperspectral reflectance (HSR), and chemometrics. The application of a spectranomic approach contributed to shedding light on the relationship between the presence of specific hydrosoluble metabolites and the optical properties of both asymptomatic Xf-infected and non-infected olive leaves. Significant correlations between wavebands located in the range of 530–560 nm and 1380–1470 nm, and the following metabolites were found to be indicative of Xf infection: malic acid, fructose, sucrose, oleuropein derivatives, and formic acid. This information is the key to the development of HSR-based sensors capable of early detection of Xf infections in olive trees. [ABSTRACT FROM AUTHOR]

Management of Xylella fastidiosa subsp. pauca ( Xfp ) presents significant challenges due to the lack of genetic resistance in major crops, pathogen variability and resistance development against the main antimicrobial compounds, and the lack of effective chemical compounds for control. Traditional bactericides in the EU are restricted, and copper-based products are increasingly limited due to environmental impacts. In this study the antibacterial side effects of some commercial fertilizers against Xfp were evaluated. These products, containing metal ions (mainly copper and/or zinc) complexed with phosphites and bioavailable silicon, show antimicrobial and bactericidal activities in vitro which suggest their possible use to control the pathogen, as well as enhanced plant resistance to biotic and abiotic stresses. Greenhouse and open field trials showed that they can significantly reduce disease severity and pathogen population, thus improving fruit yield. The integrated pest and disease management (IPDM) strategy, which combines these treatments with agronomic and phytosanitary vector-control measures, leads to a reduction of disease symptoms in treated plants compared to untreated ones. These findings highlight the potential of systemic fertilizers to mitigate Xfp symptoms by providing antimicrobial collateral effects and probably enhance plant defenses, since similar compounds are known to be plant defense inducers in other pathosystems. Therefore, these products offer a sustainable solution for managing plant pathogenic bacteria and improving crop health and yield. This approach is crucial for the sustainability of olive production in Xf -affected areas. However, further research is needed to optimize these strategies for long-term effectiveness under field conditions. Overall, the results emphasize the value of the collateral effects of some mineral fertilizers in a comprehensive strategy aimed at mitigating the symptoms of Xfp and safeguarding the agricultural productivity as well as the invaluable heritage of centuries-old Apulian olive trees.

Occurrence, seasonal abundance and diversity of Xylella fastidiosa Wells et al. potential vectors species and other Auchenorrhyncha were studied in olive orchards under different management systems. Auchenorrhyncha were monitored monthly in 6 olive groves at Istiea (Central Greece) and Chania (South Greece) for 13 months using malaise traps and sweeping-net, as a sampling strategy to collect even the most, or the least-mobile Auchenorrhyncha within the orchards. Olive orchards in Chania had a lower abundance and diversity in X. fastidiosa potential vectors, as well as in total Auchenorrhyncha. The abandoned olive orchard hosted the highest population of potential vectors in Chania, but the lowest in Istiea, compared with the respective cultivated one. The organic farms were more diverse in Auchenorrhyncha compared to the other management systems in both regions. Weed control provided the most probable explanation for the significant Auchenorrhyncha population fluctuation among olive orchards. However, insecticide applications against olive fruit fly did not affect Auchenorrhyncha abundance. The conventional orchard in Istiea displayed the highest abundance and species richness of the potential vectors of X. fastidiosa, mainly during autumn, when dried weeds remained in the orchard after herbicide application. [ABSTRACT FROM AUTHOR]

The colonization behavior of the Xylella fastidiosa strain CoDiRO, the causal agent of olive quick decline syndrome (OQDS), within the xylem of Olea europaea L. is still quite controversial. As previous literature suggests, even if xylem vessel occlusions in naturally infected olive plants were observed, cell aggregation in the formation of occlusions had a minimal role. This observation left some open questions about the whole behavior of the CoDiRO strain and its actual role in OQDS pathogenesis. In order to evaluate the extent of bacterial infection in olive trees and the role of bacterial aggregates in vessel occlusions, we tested a specific fluorescence in situ hybridization (FISH) probe (KO 210) for X. fastidiosa and quantified the level of infection and vessel occlusion in both petioles and branches of naturally infected and non-infected olive trees. All symptomatic petioles showed colonization by X. fastidiosa, especially in the larger innermost vessels. In several cases, the vessels appeared completely occluded by a biofilm containing bacterial cells and extracellular matrix and the frequent colonization of adjacent vessels suggested a horizontal movement of the bacteria. Infected symptomatic trees had 21.6 ± 10.7% of petiole vessels colonized by the pathogen, indicating an irregular distribution in olive tree xylem. Thus, our observations point out the primary role of the pathogen in olive vessel occlusions. Furthermore, our findings indicate that the KO 210 FISH probe is suitable for the specific detection of X. fastidiosa.

The meadow froghopper, Philaenus spumarius L., is endemic in Italy and was not considered a harmful species until 2014, when the olive quick decline syndrome (OQDS) showed up in Apulia (southern Italy). It was immediately suspected and then verified as the main vector of Xylella fastidiosa, the bacterium responsible for the disease. Currently, EU Directives consider the fight against P. spumarius compulsory in member states and recommend Integrated Pest Management (IPM), both in uncultivated and cultivated infested areas, to minimise the environmental impact of chemical pesticides. This should be based on an improved knowledge of the vector with its seasonal trends and feeding habits linked to specific herbaceous species. In this context, our field study was aimed to improve the understanding of the vector nutritional behaviour, especially at its critical nymph stage, by monitoring its presence on different herbaceous target species, using its typical feeding foams as key indicator. The study area was in Lazio region (central Italy), dedicated to olive growing and still unaffected by the X. fastidiosa plague. Over two years, during the nymph development period, field data have been acquired over the test area and then analysed by coupling statistical (ANOVA), geographical information system (GIS) and geo-referenced field sampling approaches. Results highlighted that P. spumarius exhibits significant preferences for specific herbaceous plants, especially at its early development stages, detectable by tenuous spittle. This indicates female oviposition activity, which seems also not influenced by olive tree proximity. Furthermore, the non-host plant species identified here could be suitable for creating green barriers for limiting the vector diffusion to contiguous areas where sensible plantations are growing. In the final section, applied implications arising from the present findings for P. spumarius population management are discussed. [ABSTRACT FROM AUTHOR]

The colonization behavior of the Xylella fastidiosa strain CoDiRO, the causal agent of olive quick decline syndrome (OQDS), within the xylem of Olea europaea L. is still quite controversial. As previous literature suggests, even if xylem vessel occlusions in naturally infected olive plants were observed, cell aggregation in the formation of occlusions had a minimal role. This observation left some open questions about the whole behavior of the CoDiRO strain and its actual role in OQDS pathogenesis. In order to evaluate the extent of bacterial infection in olive trees and the role of bacterial aggregates in vessel occlusions, we tested a specific fluorescence in situ hybridization (FISH) probe (KO 210) for X. fastidiosa and quantified the level of infection and vessel occlusion in both petioles and branches of naturally infected and non-infected olive trees. All symptomatic petioles showed colonization by X. fastidiosa, especially in the larger innermost vessels. In several cases, the vessels appeared completely occluded by a biofilm containing bacterial cells and extracellular matrix and the frequent colonization of adjacent vessels suggested a horizontal movement of the bacteria. Infected symptomatic trees had 21.6 ± 10.7% of petiole vessels colonized by the pathogen, indicating an irregular distribution in olive tree xylem. Thus, our observations point out the primary role of the pathogen in olive vessel occlusions. Furthermore, our findings indicate that the KO 210 FISH probe is suitable for the specific detection of X. fastidiosa. [ABSTRACT FROM AUTHOR]

Xylella fastidiosa causing disease on different plant species has been reported in several European countries, since 2013. Based on multilocus sequence typing (MLST) results, there is evidence of repeated introductions of the pathogen in Spain and France. In contrast, in the Salento area of Apulia (Puglia) in Southern Italy, the existence of a unique Apulian MLST genotype of X. fastidiosa, causing the olive quick decline syndrome (OQDS; also referred to as"CoDiRO" or"ST53") was proven, and this was tentatively ascribed to X. fastidiosa subsp. pauca. In order to acquire information on intra population diversity European Food Safety Authority (EFSA) has strongly called for the characterization of X. fastidiosa isolates from Apulia to produce the necessary data to better understand strain diversity and evolution. In this work, for the first time the existence of sub-variants within a set of 14"ST53" isolates of X. fastidiosa collected from different locations was searched using DNA typing methods targeting the whole pathogen genome. Invariably, VNTR, RAPD and rep-PCR (ERIC and BOX motifs) analyses indicated that all tested isolates possessed the same genomic fingerprint, supporting the existence of predominant epidemiological strain in Apulia. To further explore the degree of clonality within this population, two isolates from two different Salento areas (Taviano and Ugento) were completely sequenced using PacBio SMRT technology. The whole genome map and sequence comparisons revealed that both isolates are nearly identical, showing less than 0.001% nucleotide diversity. However, the complete and circularized Salento-1 and Salento-2 genome sequences were different, in genome and plasmid size, from the reference strain 9a5c of X. fastidiosa subsp. pauca (from citrus), and showed a PCR-proved large genome inversion of about 1.7 Mb. Genome-wide indices ANIm and dDDH indicated that the three isolates of X. fastidiosa from Salento (Apulia, Italy), namely Salento-1, Salento-2, and De Donno, whose complete genome sequence has been recently released, share a very recent common ancestor. This highlights the importance of continuous and extensive monitoring of molecular variation of this invasive pathogen to understand evolution of adaptive traits, and the necessity for adoption of all possible measures to reduce the risk of new introductions that may augment pathogen diversity. [ABSTRACT FROM AUTHOR]

A recent severe outbreak of Xylella fastidiosa associated with 'olive quick decline syndrome' (OQDS) was reported in Apulia (Southern Italy). In this study an on-site real-time loop-mediated isothermal amplification (real-time LAMP) was developed for detecting X. fastidiosa in host plants and insects. A marked simplification of the DNA extraction procedure was obtained by heating the samples in a portable Smart-Dart device and using an optimized enhancer reaction buffer. The connection to a tablet or Smartphone allowed to visualize the results of the reaction in real time. Compared to PCR and ELISA, with which it showed comparable results in terms of sensitivity and reliability in the X. fastidiosa detection, this simplified real-time LAMP procedure proved to be "user friendly", displaying the advantages to be an on-site detection method of easy handling, rapid execution and low cost. [ABSTRACT FROM AUTHOR]