Copper compounds, widely used to control plant-pathogenic bacteria, have traditionally been employed against fire blight, caused by Erwinia amylovora . However, recent studies have shown that some phytopathogenic bacteria enter into the viable-but-nonculturable (VBNC) state in the presence of copper. To determine whether copper kills E. amylovora or induces the VBNC state, a mineral medium without copper or supplemented with 0.005, 0.01, or 0.05 mM Cu ²⁺ was inoculated with 10 ⁷ CFU/ml of this bacterium and monitored over 9 months. Total and viable cell counts were determined by epifluorescence microscopy using the LIVE/DEAD kit and by flow cytometry with 5-cyano-2,3-ditolyl tetrazolium chloride and SYTO 13. Culturable cells were counted on King's B nonselective solid medium. Changes in the bacterial morphology in the presence of copper were observed by scanning electron microscopy. E. amylovora entered into the VBNC state at all three copper concentrations assayed, much faster when the copper concentration increased. The addition of different agents which complex copper allowed the resuscitation (restoration of culturability) of copper-induced VBNC cells. Finally, copper-induced VBNC cells were virulent only for the first 5 days, while resuscitated cells always regained their pathogenicity on immature fruits over 9 months. These results have shown, for the first time, the induction of the VBNC state in E. amylovora as a survival strategy against copper.

Xylella fastidiosa is an economically important plant-pathogenic bacterium that has emerged as a pathogen of global importance associated with a devastating epidemic in olive trees in Italy associated with X. fastidiosa subspecies pauca and other outbreaks in Europe, such as X. fastidiosa subspecies fastidiosa and X. fastidiosa subspecies multiplex in Spain and X. fastidiosa subspecies multiplex in France. We present evidence of multiple introductions of X. fastidiosa subspecies multiplex , likely from the United States, into Spain, Italy, and France. These introductions illustrate the risks associated with the commercial trade of plant material at global scales and the need to develop effective policy to limit the likelihood of pathogen pollution into naive regions. Our study demonstrates the need to utilize whole-genome sequence data to study X. fastidiosa introductions at outbreak stages, since a limited number of genetic markers does not provide sufficient phylogenetic resolution to determine dispersal paths or relationships among strains that are of biological and quarantine relevance.

Novel aerobic, Gram-negative bacteria with DNA G+C contents below 50 mol% were isolated from the culturable microbiota associated with the Mediterranean seagrass Posidonia oceanica. 16S rRNA gene sequence analyses revealed that they belong to the genus Marinomonas. Strain IVIA-Po-186 is a strain of the species Marinomonas mediterranea, showing 99.77 % 16S rRNA gene sequence similarity with the type strain, MMB-1^T, and sharing all phenotypic characteristics studied. This is the first description of this species forming part of the microbiota of a marine plant. A second strain, designated IVIA-Po-101^T, was closely related to M. mediterranea based on phylogenetic studies. However, it differed in characteristics such as melanin synthesis and tyrosinase, laccase and antimicrobial activities. In addition, strain IVIA-Po-101^T was auxotrophic and unable to use acetate. IVIA-Po-101^T shared 97.86 % 16S rRNA gene sequence similarity with M. mediterranea MMB-1^T, but the level of DNA–DNA relatedness between the two strains was only 10.3 %. On the basis of these data, strain IVIA-Po-101^T is considered to represent a novel species of the genus Marinomonas, for which the name Marinomonas balearica sp. nov. is proposed. The type strain is IVIA-Po-101^T (=CECT 7378^T =NCIMB 14432^T). A third novel strain, IVIA-Po-185^T, was phylogenetically distant from all recognized Marinomonas species. It shared the highest 16S rRNA gene sequence similarity (97.4 %) with the type strain of Marinomonas pontica, but the level of DNA–DNA relatedness between the two strains was only 14.5 %. A differential chemotaxonomic marker of this strain in the genus Marinomonas is the presence of the fatty acid C_17 : 0 cyclo. Strain IVIA-Po-185^T is thus considered to represent a second novel species of the genus, for which the name Marinomonas pollencensis sp. nov. is proposed. The type strain is IVIA-Po-185^T (=CECT 7375^T =NCIMB 14435^T). An emended description of the genus Marinomonas is given based on the description of these two novel species, as well as other Marinomonas species described after the original description of the genus.

Xylella fastidiosa, a quarantine organism in the European Union (EU), causes diseases in a wide variety of plants such as almond, cherry, grape, citrus, elm, olive and coffee trees and many ornamental plants. Since the detection of the bacterium in Italy (2013), where it is associated to a severe epidemic on olive trees, the pathogen has also been detected in France (2015) and Germany (2016) (EPPO, 2016). Due to the recent outbreaks and to different interceptions, the EU has implemented annual surveys in its Member States to prevent new introductions or the spread of this harmful organism. During official surveys in late autumn 2016 in Mallorca Island, Spain, some cherry and Polygala myrtifolia plants located in a garden center near the locality of Manacor showed symptoms of marginal leaf scorch, leaf chlorosis, defoliation, and general decay. DNA was extracted from leaf veins and petioles of symptomatic leaves using the CTAB extraction method (EPPO, 2016). DNA extracts were tested for the presence of X. ...

RobHortic is a remote-controlled field robot that has been developed for inspecting the presence of pests and diseases in horticultural crops using proximal sensing. The robot is equipped with colour, multispectral, and hyperspectral (400–1000 nm) cameras, located looking at the ground (towards the plants). To prevent the negative influence of direct sunlight, the scene was illuminated by four halogen lamps and protected from natural light using a tarp. A GNSS (Global Navigation Satellite System) was used to geolocate the images of the field. All sensors were connected to an on-board industrial computer. The software developed specifically for this application captured the signal from an encoder, which was connected to the motor, to synchronise the acquisition of the images with the advance of the robot. Upon receiving the signal, the cameras are triggered, and the captured images are stored along with the GNSS data. The robot has been developed and tested over three campaigns in carrot fields for the detection of plants infected with ‘Candidatus Liberibacter solanacearum’. The first two years were spent creating and tuning the robot and sensors, and data capture and geolocation were tested. In the third year, tests were carried out to detect asymptomatic infected plants. As a reference, plants were analysed by molecular analysis using a specific real-time Polymerase Chain Reaction (PCR), to determine the presence of the target bacterium and compare the results with the data obtained by the robot. Both laboratory and field tests were done. The highest match was obtained using Partial Least Squares-Discriminant Analysis PLS-DA, with a 66.4% detection rate for images obtained in the laboratory and 59.8% for images obtained in the field.

Xylella fastidiosa (Xf) is a vascular plant pathogen native to the Americas. In 2013, it was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This finding prompted mandatory surveys across Europe, successively revealing that the bacterium was already established in some distant areas of the western Mediterranean. To date, the Balearic Islands (Spain) hold the major known genetic diversity of Xf in Europe. Since October 2016, four sequence types (ST) belonging to the subspecies fastidiosa (ST1), multiplex (ST7, ST81), and pauca (ST80) have been identified infecting 28 host species, including grapevines, almond, olive, and fig trees. ST1 causes Pierce’s disease (PD) and together with ST81 are responsible for almond leaf scorch disease (ALSD) in California, from where they were introduced into Mallorca in around 1993, very likely via infected almond scions brought for grafting. To date, almond leaf scorch disease affects over 81% of almond trees and Pierce’s disease is widespread in vineyards across Mallorca, although producing on average little economic impact. In this perspective, we present and analyze a large Xf-hosts database accumulated over four years of field surveys, laboratory sample analyses, and research to understand the underlying causes of Xf emergence and spread among crops and wild plants in the Balearic Islands. The impact of Xf on the landscape is discussed.