Inferring pathogen dynamics from temporal count data: the emergence of Xylella fastidiosa in France is probably not recent.

Unravelling the ecological structure of emerging plant pathogens persisting in multi-host systems is challenging. In such systems, observations are often heterogeneous with respect to time, space and host species, and may lead to biases of perception. The biased perception of pathogen ecology may be exacerbated by hidden fractions of the whole host population, which may act as infection reservoirs. We designed a mechanistic-statistical approach to help understand the ecology of emerging pathogens by filtering out some biases of perception. This approach, based on SIR (Susceptible-Infected-Removed) models and a Bayesian framework, disentangles epidemiological and observational processes underlying temporal counting data. We applied our approach to French surveillance data on Xylella fastidiosa, a multi-host pathogenic bacterium recently discovered in Corsica, France. A model selection led to two diverging scenarios: one scenario without a hidden compartment and an introduction around 2001, and the other with a hidden compartment and an introduction around 1985. Thus, Xylella fastidiosa was probably introduced into Corsica much earlier than its discovery, and its control could be arduous under the hidden compartment scenario. From a methodological perspective, our approach provides insights into the dynamics of emerging plant pathogens and, in particular, the potential existence of infection reservoirs.

Aggressive Emerging Pathovars of Xanthomonas arboricola Represent Widespread Epidemic Clones Distinct from Poorly Pathogenic Strains, as Revealed by Multilocus Sequence Typing.

Deep and comprehensive knowledge of the genetic structure of pathogenic species is the cornerstone on which the design of precise molecular diagnostic tools is built. Xanthomonas arboricola is divided into pathovars, some of which are classified as quarantine organisms in many countries and are responsible for diseases on nut and stone fruit trees that have emerged worldwide. Recent taxonomic studies of the genus Xanthomonas showed that strains isolated from other hosts should be classified in X. arboricola, extending the host range of the species. To investigate the genetic structure of X. arboricola and the genetic relationships between highly pathogenic strains and strains apparently not relevant to plant health, we conducted multilocus sequence analyses on a collection of strains representative of the known diversity of the species. Most of the pathovars were clustered in separate monophyletic groups. The pathovars pruni, corylina, and juglandis, responsible for pandemics in specific hosts, were highly phylogenetically related and clustered in three distinct clonal complexes. In contrast, strains with no or uncertain pathogenicity were represented by numerous unrelated singletons scattered in the phylogenic tree. Depending on the pathovar, intra- and interspecies recombination played contrasting roles in generating nucleotide polymorphism. This work provides a population genetics framework for molecular epidemiological surveys of emerging plant pathogens within X. arboricola. Based on our results, we propose to reclassify three former pathovars of Xanthomonas campestris as X. arboricola pv. arracaciae comb. nov., X. arboricola pv. guizotiae comb. nov., and X. arboricola pv. zantedeschiae comb. nov. An emended description of X. arboricola Vauterin et al. 1995 is provided.

Phylogenetic and Variable-Number Tandem-Repeat Analyses Identify Nonpathogenic Xanthomonas arboricola Lineages Lacking the Canonical Type III Secretion System.

Xanthomonas arboricola is conventionally known as a taxon of plant-pathogenic bacteria that includes seven pathovars. This study showed that X. arboricola also encompasses nonpathogenic bacteria that cause no apparent disease symptoms on their hosts. The aim of this study was to assess the X. arboricola population structure associated with walnut, including nonpathogenic strains, in order to gain a better understanding of the role of nonpathogenic xanthomonads in walnut microbiota. A multilocus sequence analysis (MLSA) was performed on a collection of 100 X. arboricola strains, including 27 nonpathogenic strains isolated from walnut. Nonpathogenic strains grouped outside clusters defined by pathovars and formed separate genetic lineages. A multilocus variable-number tandem-repeat analysis (MLVA) conducted on a collection of X. arboricola strains isolated from walnut showed that nonpathogenic strains clustered separately from clonal complexes containing Xanthomonas arboricola pv. juglandis strains. Some nonpathogenic strains of X. arboricola did not contain the canonical type III secretion system (T3SS) and harbored only one to three type III effector (T3E) genes. In the nonpathogenic strains CFBP 7640 and CFBP 7653, neither T3SS genes nor any of the analyzed T3E genes were detected. This finding raises a question about the origin of nonpathogenic strains and the evolution of plant pathogenicity in X. arboricola. T3E genes that were not detected in any nonpathogenic isolates studied represent excellent candidates to be those responsible for pathogenicity in X. arboricola.

Commodity risk assessment of Petunia spp. and Calibrachoa spp. unrooted cuttings from Kenya.

The European Commission requested the EFSA Panel on Plant Health to evaluate the probability of entry of pests (likelihood of pest freedom at entry), including both regulated and non-regulated pests, associated with unrooted cuttings of the genera Petunia and Calibrachoa produced under physical isolation in Kenya. The relevance of any pest for this opinion was based on evidence following defined criteria, based on the methodology used for High-Risk Plants adapted for the specificity of this assessment. Fourteen EU-regulated pests (Bemisia tabaci, cowpea mild mottle virus, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, potato leafroll virus, potato spindle tuber viroid, Ralstonia pseudosolanacearum, R. solanacearum, Scirtothrips dorsalis, tomato mild mottle virus, tomato spotted wilt virus, tomato yellow leaf curl virus and Xanthomonas vesicatoria) and six EU non-regulated pests (Aleurodicus dispersus, pepper veinal mottle virus, Nipaecoccus viridis, Phenacoccus solenopsis, Tetranychus neocaledonicus and tomato yellow ring virus) fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Kenya were evaluated, taking into account the possible limiting factors. Additionally, an expert judgement is given on the likelihood of pest freedom, taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with T. neocaledonicus being the pest most frequently expected on the imported cuttings. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9942 and 10,000 bags containing unrooted cuttings of Petunia spp. and Calibrachoa spp. per 10,000 would be free of T. neocaledonicus.

Commodity risk assessment of Sorbus aucuparia plants from the UK.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'high risk plants, plant products and other objects'. Taking into account the available scientific information, including the technical information provided by the applicant country, this Scientific Opinion covers the plant health risks posed by the following commodities: Sorbus aucuparia bare-root plants and rooted plants in pots up to 7 years old and specimen trees in pots up to 15 years old imported into the EU from the UK. A list of pests potentially associated with the commodities was compiled. The relevance of any pest was assessed based on evidence following defined criteria. Three EU quarantine pests (Entoleuca mammata and Phytophthora ramorum (non-EU isolates), Erwinia amylovora), were selected for further evaluation. For two of the selected pests (E. mammata and P. ramorum), the risk mitigation measures implemented in the UK and specified in the technical dossier were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The degree of pest freedom varies between the pests evaluated, with P. ramorum being the pest most frequently expected on the imported S. aucuparia plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9812 and 10,000 bare-root S. aucuparia plants per 10,000 will be free from P. ramorum.

Commodity risk assessment of Petunia spp. and Calibrachoa spp. unrooted cuttings from Guatemala.

The European Commission requested the EFSA Panel on Plant Health to evaluate the probability of entry of pests (likelihood of pest freedom at entry), including both, regulated and non-regulated pests, associated with unrooted cuttings of the genera Petunia and Calibrachoa produced under physical isolation in Guatemala. The relevance of any pest for this opinion was based on evidence following defined criteria, based on the methodology used for high-risk plants adapted for the specificity of this assessment. Nineteen EU regulated pests (Bemisia tabaci, pepper golden mosaic virus, pepper huasteco yellow vein virus, tomato severe leaf curl virus, tomato yellow leaf curl virus, tomato spotted wilt virus, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, Bactericera cockerelli, Eotetranichus lewisi, Epitrix subcrinita, Epitrix cucumeris, Helicoverpa zea, Chloridea virescens, Spodoptera ornithogalli, Ralstonia solanacearum, Ralstonia pseudosolanacearum, Xanthomonas vesicatoria) and one EU non-regulated (Phenacoccus solenopsis) pest fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Guatemala were evaluated taking into account the possible limiting factors, and an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The limited and partially conflicting information provided in the dossier contributes to the wide estimates of pest freedom. The estimated degree of pest freedom varies among the pests evaluated, with Ralstonia spp. (R. solanacearum and R. pseudosolanacearum) being the pest most frequently expected on the imported cuttings. The expert knowledge elicitation indicated, with 95% certainty, that between 9916 and 10,000 bags containing unrooted cuttings per 10,000 would be free of Ralstonia spp.

Commodity risk assessment of Cornus alba and Cornus sanguinea plants from the UK.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as 'high risk plants, plant products and other objects'. Taking into account the available scientific information, including the technical information provided by the applicant country, this Scientific Opinion covers the plant health risks posed by the following commodities: Cornus alba and Cornus sanguinea bare-root plants and rooted plants in pots up to 7 years old imported into the EU from the UK. A list of pests potentially associated with the commodities was compiled. The relevance of any pest was assessed based on evidence following defined criteria. Four EU quarantine pests (Meloidogyne fallax, Phytophthora ramorum (non-EU isolates), tobacco ringspot virus, and tomato ringspot virus) and one EU non-regulated pest (Discula destructiva), were selected for further evaluation. For the selected pests, the risk mitigation measures implemented in the technical dossier from the UK were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The degree of pest freedom varies among the pests evaluated, with P. ramorum being the pest most frequently expected on the imported C. alba and C. sanguinea plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9823 and 10,000 bare-root C. alba and C. sanguinea plants per 10,000 will be free from P. ramorum.

Genome sequence of Xanthomonas fuscans subsp. fuscans strain 4834-R reveals that flagellar motility is not a general feature of xanthomonads.

BACKGROUND: Xanthomonads are plant-associated bacteria responsible for diseases on economically important crops. Xanthomonas fuscans subsp. fuscans (Xff) is one of the causal agents of common bacterial blight of bean. In this study, the complete genome sequence of strain Xff 4834-R was determined and compared to other Xanthomonas genome sequences. RESULTS: Comparative genomics analyses revealed core characteristics shared between Xff 4834-R and other xanthomonads including chemotaxis elements, two-component systems, TonB-dependent transporters, secretion systems (from T1SS to T6SS) and multiple effectors. For instance a repertoire of 29 Type 3 Effectors (T3Es) with two Transcription Activator-Like Effectors was predicted. Mobile elements were associated with major modifications in the genome structure and gene content in comparison to other Xanthomonas genomes. Notably, a deletion of 33 kbp affects flagellum biosynthesis in Xff 4834-R. The presence of a complete flagellar cluster was assessed in a collection of more than 300 strains representing different species and pathovars of Xanthomonas. Five percent of the tested strains presented a deletion in the flagellar cluster and were non-motile. Moreover, half of the Xff strains isolated from the same epidemic than 4834-R was non-motile and this ratio was conserved in the strains colonizing the next bean seed generations. CONCLUSIONS: This work describes the first genome of a Xanthomonas strain pathogenic on bean and reports the existence of non-motile xanthomonads belonging to different species and pathovars. Isolation of such Xff variants from a natural epidemic may suggest that flagellar motility is not a key function for in planta fitness.

Genomic insights into strategies used by Xanthomonas albilineans with its reduced artillery to spread within sugarcane xylem vessels.

BACKGROUND: Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy compared to other species of Xanthomonas. For example, this species produces a potent DNA gyrase inhibitor called albicidin that is largely responsible for inducing disease symptoms; its habitat is limited to xylem; and the species exhibits large variability. A first manuscript on the complete genome sequence of the highly pathogenic X. albilineans strain GPE PC73 focused exclusively on distinctive genomic features shared with Xylella fastidiosa-another xylem-limited Xanthomonadaceae. The present manuscript on the same genome sequence aims to describe all other pathogenicity-related genomic features of X. albilineans, and to compare, using suppression subtractive hybridization (SSH), genomic features of two strains differing in pathogenicity. RESULTS: Comparative genomic analyses showed that most of the known pathogenicity factors from other Xanthomonas species are conserved in X. albilineans, with the notable absence of two major determinants of the "artillery" of other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis gene cluster, and the type III secretion system Hrp (hypersensitive response and pathogenicity). Genomic features specific to X. albilineans that may contribute to specific adaptation of this pathogen to sugarcane xylem vessels were also revealed. SSH experiments led to the identification of 20 genes common to three highly pathogenic strains but missing in a less pathogenic strain. These 20 genes, which include four ABC transporter genes, a methyl-accepting chemotaxis protein gene and an oxidoreductase gene, could play a key role in pathogenicity. With the exception of hypothetical proteins revealed by our comparative genomic analyses and SSH experiments, no genes potentially involved in any offensive or counter-defensive mechanism specific to X. albilineans were identified, supposing that X. albilineans has a reduced artillery compared to other pathogenic Xanthomonas species. Particular attention has therefore been given to genomic features specific to X. albilineans making it more capable of evading sugarcane surveillance systems or resisting sugarcane defense systems. CONCLUSIONS: This study confirms that X. albilineans is a highly distinctive species within the genus Xanthomonas, and opens new perpectives towards a greater understanding of the pathogenicity of this destructive sugarcane pathogen.

Type three effector gene distribution and sequence analysis provide new insights into the pathogenicity of plant-pathogenic Xanthomonas arboricola.

Xanthomonas arboricola is a complex bacterial species which mainly attacks fruit trees and is responsible for emerging diseases in Europe. It comprises seven pathovars (X. arboricola pv. pruni, X. arboricola pv. corylina, X. arboricola pv. juglandis, X. arboricola pv. populi, X. arboricola pv. poinsettiicola, X. arboricola pv. celebensis, and X. arboricola pv. fragariae), each exhibiting characteristic disease symptoms and distinct host specificities. To better understand the factors underlying this ecological trait, we first assessed the phylogenetic relationships among a worldwide collection of X. arboricola strains by sequencing the housekeeping gene rpoD. This analysis revealed that strains of X. arboricola pathovar populi are divergent from the main X. arboricola cluster formed by all other strains. Then, we investigated the distribution of 53 type III effector (T3E) genes in a collection of 57 X. arboricola strains that are representative of the main X. arboricola cluster. Our results showed that T3E repertoires vary greatly between X. arboricola pathovars in terms of size. Indeed, X. arboricola pathovars pruni, corylina, and juglandis, which are responsible for economically important stone fruit and nut diseases in Europe, harbored the largest T3E repertoires, whereas pathovars poinsettiicola, celebensis, and fragariae harbored the smallest. We also identified several differences in T3E gene content between X. arboricola pathovars pruni, corylina, and juglandis which may account for their differing host specificities. Further, we examined the allelic diversity of eight T3E genes from X. arboricola pathovars. This analysis revealed very limited allelic variations at the different loci. Altogether, the data presented here provide new insights into the evolution of pathogenicity and host range of X. arboricola and are discussed in terms of emergence of new diseases within this bacterial species.

Commodity risk assessment of Jasminum polyanthum unrooted cuttings from Uganda.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation EU/2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by unrooted cuttings of Jasminum polyanthum that are imported from Uganda, taking into account the available scientific information, including the technical information provided by the NPPO of Uganda. The relevance of any pest for this opinion was based on evidence following defined criteria. Six species, two EU-regulated pests (Bemisia tabaci, non-European populations and Scirtothrips dorsalis) and four EU non-regulated pests (Coccus viridis, Diaphania indica, Pulvinaria psidii and Selenaspidus articulatus), fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Uganda were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with B. tabaci and S. dorsalis being the pests most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,950 and 10,000 plants per 10,000 would be free of B. tabaci.

Commodity risk assessment of specified species of Lonicera potted plants from Turkey.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in the Commission Implementing Regulation (EU) 2018/2019 as 'High-risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by potted plants (2-4 years old) of specified Lonicera species produced in nurseries and that are imported from Turkey, taking into account the available scientific information, including the technical information provided by the NPPO of Turkey. The relevance of any pest for this Opinion was based on evidence following defined criteria listed in Section 4.1. Three species, the EU-quarantine pests Lopholeucaspis japonica and Meloidogyne chitwoodi and the protected zone quarantine pest Bemisia tabaci, fulfilled these criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Turkey were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with B. tabaci on evergreen species of Lonicera spp. being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,293 and 10,000 plants per 10,000 would be free of B. tabaci.

Commodity risk assessment of Berberis thunbergii potted plants from Turkey.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in the Commission Implementing Regulation (EU) 2018/2019 as 'High-risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by potted plants (2-3 years old) of Berberis thunbergii produced in nurseries and imported into the EU from Turkey, taking into account the available scientific information, including the technical information provided by the NPPO of Turkey. The relevance of any pest for this Opinion was based on evidence following defined criteria. Two species, the EU-quarantine pest Bemisia tabaci and the non-regulated pest Malacosoma parallela, fulfilled the relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Turkey were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with B. tabaci being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,928 and 10,000 plants per 10,000 would be free of B. tabaci. The role of Berberis thunbergii as possible host of Puccinia spp. is discussed in the body of the opinion.

Sensing and adhesion are adaptive functions in the plant pathogenic xanthomonads.

BACKGROUND: Bacterial plant pathogens belonging to the Xanthomonas genus are tightly adapted to their host plants and are not known to colonise other environments. The host range of each strain is usually restricted to a few host plant species. Bacterial strains responsible for the same type of symptoms on the same host range cluster in a pathovar. The phyllosphere is a highly stressful environment, but it provides a selective habitat and a source of substrates for these bacteria. Xanthomonads colonise host phylloplane before entering leaf tissues and engaging in an invasive pathogenic phase. Hence, these bacteria are likely to have evolved strategies to adapt to life in this environment. We hypothesised that determinants responsible for bacterial host adaptation are expressed starting from the establishment of chemotactic attraction and adhesion on host tissue. RESULTS: We established the distribution of 70 genes coding sensors and adhesins in a large collection of xanthomonad strains. These 173 strains belong to different pathovars of Xanthomonas spp and display different host ranges. Candidate genes are involved in chemotactic attraction (25 genes), chemical environment sensing (35 genes), and adhesion (10 genes). Our study revealed that candidate gene repertoires comprised core and variable gene suites that likely have distinct roles in host adaptation. Most pathovars were characterized by unique repertoires of candidate genes, highlighting a correspondence between pathovar clustering and repertoires of sensors and adhesins. To further challenge our hypothesis, we tested for molecular signatures of selection on candidate genes extracted from sequenced genomes of strains belonging to different pathovars. We found strong evidence of adaptive divergence acting on most candidate genes. CONCLUSIONS: These data provide insight into the potential role played by sensors and adhesins in the adaptation of xanthomonads to their host plants. The correspondence between repertoires of sensor and adhesin genes and pathovars and the rapid evolution of sensors and adhesins shows that, for plant pathogenic xanthomonads, events leading to host specificity may occur as early as chemotactic attraction by host and adhesion to tissues.

Commodity risk assessment of Robinia pseudoacacia plants from Turkey.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation EU/2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by bare rooted and potted plants of Robinia pseudoacacia that are imported from Turkey, taking into account the available scientific information, including the technical information provided by the Turkish NPPO. The relevance of any pest for this opinion was based on evidence following defined criteria. Three species, the EU-quarantine pests Anoplophora chinensis and Lopholeucapsis japonica, and the EU non-regulated pest Phocazia shantungensis fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Turkey were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with L. japonica being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,521 and 10,000 plants per 10,000 would be free of L. japonica.

Commodity risk assessment of Nerium oleander plants from Turkey.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation EU/2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers plant health risks posed by bare rooted and potted plants of Nerium oleander that are imported from Turkey, taking into account the available scientific information, including the technical information provided by the Turkish NPPO. The relevance of any pest for this opinion was based on evidence following defined criteria. One species, the EU non-regulated pest Phenacoccus solenopsis, fulfilled all relevant criteria and was selected for further evaluation. For this pest, the risk mitigation measures proposed in the technical dossier from Turkey were evaluated taking into account the possible limiting factors. For this pest, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,719 and 10,000 plants per 10,000 would be free of P. solenopsis.

Commodity risk assessment of Robinia pseudoacacia plants from Israel.

The EFSA Panel on Plant Health was requested to prepare and deliver risk assessments for commodities listed in the relevant Implementing Acts as 'High risk plants, plant products and other objects' [Commission Implementing Regulation (EU) 2018/2019 establishing a provisional list of high risk plants, plant products or other objects, within the meaning of Article 42 of Regulation (EU) 2016/2031]. The current Scientific Opinion covers all plant health risks posed by bare rooted plants for planting of Robinia pseudoacacia (1 year old with a stem diameter of less than 2.5 cm) imported from Israel, taking into account the available scientific information, including the technical information provided by Israel by 26 December 2019. The relevance of an EU-quarantine pest for this opinion was based on evidence that: (i) the pest is present in Israel; (ii) R. pseudoacacia is a host of the pest, and (iii) the pest can be associated with the commodity. The relevance of this opinion for other non EU-regulated pests was based on evidence that: (i) the pest is present in Israel (ii) the pest is absent in the EU; (iii) R. pseudoacacia is a host of the pest; (iv) the pest can be associated with the commodity and (v) the pest may have an impact and can pose a potential risk for the EU territory. Two pests (one insect and one fungus, Euwallacea fornicatus and Fusarium euwallaceae) that fulfilled all criteria were selected for further evaluation. For the two selected pests, the risk mitigation measures proposed in the technical dossier from Israel were evaluated. Limiting factors in the effectiveness of the measures were documented. For the selected pests an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment, therefore the Panel is 95% sure that 9,950 or more plants per 10,000 will be free from these two pests.

Commodity risk assessment of Jasminum polyanthum plants from Israel.

The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation EU/2018/2019 as 'High risk plants, plant products and other objects'. This Scientific Opinion covers all plant health risks posed by unrooted cuttings of Jasminum polyanthum produced in a protected environment (greenhouse) that are imported from Israel, taking into account the available scientific information, including the technical information provided by the NPPO of Israel by 15 March 2020. The relevance of an EU quarantine pest for this opinion was based on evidence that: (i) the pest is present in Israel; (ii) Jasminum is a host of the pest; and (iii) the pest can be associated with the commodity. The relevance of any other pest, not regulated in the EU, was based on evidence that: (i) the pest is present in Israel; (ii) the pest is absent in the EU; (iii) Jasminum is a host of the pest; (iv) the pest can be associated with the commodity and (v) the pest may have an impact and can pose a potential risk for the EU territory. Six species, the EU-quarantine pest Scirtothrips dorsalis, and the EU non-regulated pests Aonidiella orientalis, Milviscutulus mangiferae, Paracoccus marginatus, Pulvinaria psidii and Colletotrichum siamense fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Israel were evaluated taking into account the possible limiting factors. For these pests, an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The estimated degree of pest freedom varies among the pests evaluated, with S. dorsalis being the pest most frequently expected on the imported plants. The Expert Knowledge Elicitation indicated, with 95% certainty, that between 9,958 and 10,000 bags per 10,000 would be free of S. dorsalis.

Commodity risk assessment of Albizia julibrissin plants from Israel.

The EFSA Panel on Plant Health was requested to prepare and deliver risk assessments for commodities listed in the relevant Implementing Acts as 'High risk plants, plant products and other objects' [Commission Implementing Regulation (EU) 2018/2019 establishing a provisional list of high-risk plants, plant products or other objects, within the meaning of Article 42 of Regulation (EU) 2016/2031]. The current Scientific Opinion covers all plant health risks posed by Albizia julibrissin imported from Israel, taking into account the available scientific information, including the technical information provided by Israel. The relevance of an EU-regulated pest for this opinion was based on evidence that: (i) the pest is present in Israel; (ii) A. julibrissin is a host of the pest and (iii) the pest can be associated with the commodity. The relevance of this opinion for other non EU-regulated pests was based on evidence that (i) the pest is present in Israel; (ii) the pest is absent in the EU; (iii) A. julibrissin is a host of the pest; (iv) the pest can be associated with the commodity and (v) the pest may have an impact and can pose a potential risk for the EU territory. Three pests (two insects, Aonidiella orientalis and Euwallacea fornicatus; one fungus, Fusarium euwallaceae) that fulfilled all criteria were selected for further evaluation. For the three selected pests, the risk mitigation measures proposed in the technical dossier were evaluated. Limiting factors on the effectiveness of the measures were documented. For the selected pests, an expert judgement on the likelihood of pest freedom is given taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The Panel is 95% sure that 9,950 or more units per 10,000 will be pest free from these three pests.

The complete genome sequence of Xanthomonas albilineans provides new insights into the reductive genome evolution of the xylem-limited Xanthomonadaceae.

BACKGROUND: The Xanthomonadaceae family contains two xylem-limited plant pathogenic bacterial species, Xanthomonas albilineans and Xylella fastidiosa. X. fastidiosa was the first completely sequenced plant pathogen. It is insect-vectored, has a reduced genome and does not possess hrp genes which encode a Type III secretion system found in most plant pathogenic bacteria. X. fastidiosa was excluded from the Xanthomonas group based on phylogenetic analyses with rRNA sequences. RESULTS: The complete genome of X. albilineans was sequenced and annotated. X. albilineans, which is not known to be insect-vectored, also has a reduced genome and does not possess hrp genes. Phylogenetic analysis using X. albilineans genomic sequences showed that X. fastidiosa belongs to the Xanthomonas group. Order of divergence of the Xanthomonadaceae revealed that X. albilineans and X. fastidiosa experienced a convergent reductive genome evolution during their descent from the progenitor of the Xanthomonas genus. Reductive genome evolutions of the two xylem-limited Xanthomonadaceae were compared in light of their genome characteristics and those of obligate animal symbionts and pathogens. CONCLUSION: The two xylem-limited Xanthomonadaceae, during their descent from a common ancestral parent, experienced a convergent reductive genome evolution. Adaptation to the nutrient-poor xylem elements and to the cloistered environmental niche of xylem vessels probably favoured this convergent evolution. However, genome characteristics of X. albilineans differ from those of X. fastidiosa and obligate animal symbionts and pathogens, indicating that a distinctive process was responsible for the reductive genome evolution in this pathogen. The possible role in genome reduction of the unique toxin albicidin, produced by X. albilineans, is discussed.