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Abstract The goal was to investigate biochars’ potential as carrier for commercial Trichoderma-based biopesticides, facilitating their application in soil or growing media. Thirty-five biochars produced from various feedstocks and pyrolysis temperatures were chemically characterized. Incubation and cold storage tests using a commercial Trichoderma-based biopesticide were done. Properties leading to good Trichoderma carrier capacity (TCC) are wood-based feedstocks and low pyrolysis temperatures (p

Chitin has proven to be a valuable alternative to mineral fertilizers in growing media. We recently hypothesized that chitin might work as a biostimulant, attracting plant growth-promoting microbes to the rhizosphere. In particular, Mortierellales species increase in abundance massively with chitin application and might have a profound role in chitin-mediated plant growth promotion. We isolated four strains of this order classified as Linnemannia elongata from chitin-enriched growing medium and the lettuce rhizosphere. The isolates induced a consistent increase in shoot and root fresh weight and increased chlorophyll content of Arabidopsis thaliana in vitro, as measured by multispectral imaging. By studying the isolate's genomes, we postulated that this growth promotion was induced through auxin production, translocation of calcium to the plant, or both. The synergy between chitin and L. elongata was demonstrated by (i) the chitinase activity and chitin degradation potential of all isolates and (ii) the positive effect of chitin and L. elongata seed coating on germination of A. thaliana seeds compared with L. elongata seed coating without chitin. We conclude that chitin-related growth promotion is dependent on activation of the microbial community, with L. elongata as a key species. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Abstract 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 Costa Rica. The relevance of any pest for this opinion was based on evidence collected according to specific criteria, following the methodology used for high‐risk plants adapted for the specificity of this assessment. Twenty‐two EU regulated pests (beet curly top virus, Bemisia tabaci, Chloridea virescens, Eotetranychus lewisi, Epitrix cucumeris, Epitrix tuberis, euphorbia mosaic virus, Helicoverpa zea, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, pepper golden mosaic virus, potato spindle tuber viroid, Ralstonia pseudosolanacearum, Ralstonia solanacearum, Spodoptera ornithogalli, squash leaf curl virus, Thrips palmi, tomato golden mosaic virus, tomato leaf curl Sinaloa virus, tomato spotted wilt virus, tomato yellow leaf curl virus) and one pest that is not regulated in the EU (Aleurodicus dispersus) fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Costa Rica were evaluated taking into account possible factors limiting their efficacies. 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 tomato spotted wilt virus being the pest most frequently expected on the imported cuttings. The expert knowledge elicitation indicated, with 95% certainty that between 9927 and 10,000 bags containing unrooted cuttings of Petunia spp. and Calibrachoa spp. per 10,000 would be free of tomato spotted wilt virus.

Abstract 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.

Abstract 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.

Abstract 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.

Abstract 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. Twenty EU regulated pests (Bemisia tabaci, pepper golden mosaic virus, pepper huasteco yellow vein virus, squash leaf curl virus, tomato severe leaf curl virus, tomato yellow leaf curl virus, tomato spotted wilt virus, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, Bactericera cockerelli, Eotetranychus 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.

Nature management residues (i.e., biomass generated from the management of nature reserves) are promising peat alternatives for horticultural substrates and may have a positive effect on disease suppression because of their microbiological characteristics. Moreover, addition of fertilizer may also affect the rhizosphere microbiome and, accordingly, disease suppression. In this study, we determined the effect of two management residues in horticultural substrates (i.e., chopped heath and acidified soft rush) and two fertilization regimes (i.e., pure nitrogen fertilizer and compound fertilizer) on the suppression of Phytophthora spp. on Chamaecyparis lawsoniana. The bacterial and fungal rhizosphere community was characterized using 16S ribosomal RNA and internal transcribed spacer 2 gene metabarcoding. Soft rush with a compound fertilizer (R2) and chopped heath with a pure nitrogen fertilizer (H1) showed a disease-suppressive effect and showed the largest shifts in microbial community composition compared with peat-based substrates. The disease-suppressive treatments showed differences in their microbial communities. Different genera associated with described biocontrol agents for Phytophthora spp. were found in higher amounts in those treatments. Aspergillus and Trichoderma spp. were highly abundant in H1, while Actinomadura and Bacillus spp. had a high abundance in R2. In addition, the relative abundances of 24 bacterial and 9 fungal genera were negatively correlated with disease severity. Several of those genera, including Bacillus, Chaetomium, and Actinomadura, were significantly more abundant in one of the disease-suppressive treatments. This study shows that disease suppressiveness in sustainable horticultural substrates is dependent on fertilization and can be linked to changes in the microbial rhizosphere communities.

Abstract 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: Crataegus monogyna bare root plants and rooted plants in pots 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. Only the quarantine pest Erwinia amylovora was selected for further evaluation. For E. amylovora the special requirements specified in the Commission Implementing Regulation (EU) 2019/2072 are fulfilled by the UK and no other pests for further evaluation were selected.

A massive amount of crustaceans and bivalves are consumed each year, leading to millions of tons of processing side streams from the seafood industry. Considering the current trend of (bio)circular and zero-waste food production, crustacean and bivalve processing side streams (CBPS) seem a promising and emerging resource for producing high-value-added products. This paper highlights the general composition of CBPS with high commercial values, namely, protein, lipids, carotenoids, minerals and chitins. The extraction strategies of these fractions, including conventional chemical and environmentally friendly methods, are also discussed. This review presents and summarises CBPS as raw materials for developing fast time-to-market products complying with specific EU regulations, including animal feeds, bio-pesticide/stimulants, and cosmetic ingredients. This paper also provides insights into challenges of applying CBPS as raw materials to generate products for human consumption.

Summary Phosphorus (P) is despite its omnipresence in soils often unavailable for plants. Rhizobacteria able to solubilize P are therefore crucial to avoid P deficiency. Selection for phosphate‐solubilizing bacteria (PSB) is frequently done in vitro; however, rhizosphere competence is herein overlooked. Therefore, we developed an in planta enrichment concept enabling simultaneous microbial selection for P‐solubilization and rhizosphere competence. We used an ecologically relevant combination of iron‐ and aluminium phosphate to select for PSB in maize (Zea mays L.). In each consecutive enrichment, plant roots were inoculated with rhizobacterial suspensions from plants that had grown in substrate with insoluble P. To assess the plants’ P statuses, non‐destructive multispectral imaging was used for quantifying anthocyanins, a proxy for maize’s P status. After the third consecutive enrichment, plants supplied with insoluble P and inoculated with rhizobacterial suspensions showed a P status similar to plants supplied with soluble P. A parallel metabarcoding approach uncovered that the improved P status in the third enrichment coincided with a shift in the rhizobiome towards bacteria with plant growth‐promoting and P‐solubilizing capacities. Finally, further consecutive enrichment led to a functional relapse hallmarked by plants with a low P status and a second shift in the rhizobiome at the level of Azospirillaceae and Rhizobiaceae.

Crop diversification in spatial and temporal patterns can optimize the synchronization of nutrients plant demand and availability in soils, as plant diversity and soil microbial communities are the main drivers of biogeochemical C and nutrient cycling. The introduction of multi-cropping in organic vegetable production can represent a key strategy to ensure efficient complementation mediated by soil microbiota, including beneficial mycorrhizal fungi. This study shows the effect of the introduction of multi-cropping in five European organic vegetable systems (South-West: Italy; North-West: Denmark and Belgium; North-East: Finland and Latvia) on: (i) soil physicochemical parameters; (ii) soil microbial biomass stoichiometry; (iii) crop root mycorrhization; (iv) bacterial and fungal diversity and composition in crop rhizosphere; (v) relative abundance of selected fungal pathogens species. In each site, three cropping systems were considered: (1) crop 1—monocropping; (2) crop 2—monocropping; (3) crop 1—crop 2—intercropping or strip cropping. Results showed that, just before harvest, multi-cropping can increase soil microbial biomass amount and shape microbial community toward a predominance of some bacteria or fungi phyla, in the function of soil nutrient availability. We mainly observed a selection effect of crop type on rhizosphere microbiota. Particularly, Bacteroidetes and Mortierellomycota relative abundances in rhizosphere soil resulted in suitable ecological indicators of the positive effect of plant diversity in field, the first ones attesting an improved C and P cycles in soil and the second ones a reduced soil pathogens' pressure. Plant diversity also increased the root mycorrhizal colonization between the intercropped crops that, when properly selected, can also reduce the relative abundance of potential soil-borne pathogens, with a positive effect on crop productivity in long term.

Sustainable peat alternatives, such as composts and management residues, are considered to have beneficial microbiological characteristics compared to peat-based substrates. Studies comparing microbiological characteristics of these three types of biomass are, however, lacking. This study examined if and how microbiological characteristics of subtypes of composts and management residues differ from peat-based substrates, and how feedstock and (bio)chemical characteristics drive these characteristics. In addition, microbiome characteristics were evaluated that may contribute to plant growth and health. These characteristics include: genera associated with known beneficial or harmful microorganisms, microbial diversity, functional diversity/activity, microbial biomass, fungal to bacterial ratio and inoculation efficiency with the biocontrol fungus Trichoderma harzianum. Bacterial and fungal communities were studied using 16S rRNA and ITS2 gene metabarcoding, community-level physiological profiling (Biolog EcoPlates) and PLFA analysis. Inoculation with T. harzianum was assessed using qPCR. Samples of feedstock-based subtypes of composts and peat-based substrates showed similar microbial community compositions, while subtypes based on management residues were more variable in their microbial community composition. For management residues, a classification based on pH and hemicellulose content may be relevant for bacterial and fungal communities, respectively. Green composts, vegetable, fruit and garden composts and woody composts show the most potential to enhance plant growth or to suppress pathogens for non-acidophilic plants, while grass clippings, chopped heath and woody fractions of compost show the most potential for blends for calcifuge plants. Fungal biomass was a suitable predictor for inoculation efficiency of composts and management residues.

Abstract 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.

Abstract 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.

Abstract Background Microorganisms are not only indispensable to ecosystem functioning, they are also keystones for emerging technologies. In the last 15 years, the number of studies on environmental microbial communities has increased exponentially due to advances in sequencing technologies, but the large amount of data generated remains difficult to analyze and interpret. Recently, metabarcoding analysis has shifted from clustering reads using Operational Taxonomical Units (OTUs) to Amplicon Sequence Variants (ASVs). Differences between these methods can seriously affect the biological interpretation of metabarcoding data, especially in ecosystems with high microbial diversity, as the methods are benchmarked based on low diversity datasets. Results In this work we have thoroughly examined the differences in community diversity, structure, and complexity between the OTU and ASV methods. We have examined culture-based mock and simulated datasets as well as soil- and plant-associated bacterial and fungal environmental communities. Four key findings were revealed. First, analysis of microbial datasets at family level guaranteed both consistency and adequate coverage when using either method. Second, the performance of both methods used are related to community diversity and sample sequencing depth. Third, differences in the method used affected sample diversity and number of detected differentially abundant families upon treatment; this may lead researchers to draw different biological conclusions. Fourth, the observed differences can mostly be attributed to low abundant (relative abundance

Abstract Background When maize (Zea mays L.) is grown in the Northern hemisphere, its development is heavily arrested by chilling temperatures, especially at the juvenile phase. As some endophytes are beneficial for plants under stress conditions, we analyzed the impact of chilling temperatures on the root microbiome and examined whether microbiome-based analysis might help to identify bacterial strains that could promote growth under these temperatures. Results We investigated how the maize root microbiome composition changed by means of 16S rRNA gene amplicon sequencing when maize was grown at chilling temperatures in comparison to ambient temperatures by repeatedly cultivating maize in field soil. We identified 12 abundant and enriched bacterial families that colonize maize roots, consisting of bacteria recruited from the soil, whereas seed-derived endophytes were lowly represented. Chilling temperatures modified the root microbiome composition only slightly, but significantly. An enrichment of several chilling-responsive families was detected, of which the Comamonadaceae and the Pseudomonadaceae were the most abundant in the root endosphere of maize grown under chilling conditions, whereas only three were strongly depleted, among which the Streptomycetaceae. Additionally, a collection of bacterial strains isolated from maize roots was established and a selection was screened for growth-promoting effects on juvenile maize grown under chilling temperatures. Two promising strains that promoted maize growth under chilling conditions were identified that belonged to the root endophytic bacterial families, from which the relative abundance remained unchanged by variations in the growth temperature. Conclusions Our analyses indicate that chilling temperatures affect the bacterial community composition within the maize root endosphere. We further identified two bacterial strains that boost maize growth under chilling conditions. Their identity revealed that analyzing the chilling-responsive families did not help for their identification. As both strains belong to root endosphere enriched families, visualizing and comparing the bacterial diversity in these communities might still help to identify new PGPR strains. Additionally, a strain does not necessarely need to belong to a high abundant family in the root endosphere to provoke a growth-promoting effect in chilling conditions. Video abstract.

With nematicides progressively being banned due to their environmental impact, an urgent need for novel and sustainable control strategies has arisen. Stimulation of plant immunity, a phenomenon referred to as “induced resistance” (IR), is a promising option. In this study, Cucurbitaceae COld Peeling Extracts (CCOPEs) were shown to protect rice (Oryza sativa) and tomato (Solanum lycopersicum) against the root-knot nematodes Meloidogyne graminicola and Meloidogyne incognita, respectively. Focusing on CCOPE derived from peels of melon (Cucumis melo var. cantalupensis; mCOPE), we unveiled that this extract combines an IR-triggering capacity with direct nematicidal effects. Under lab conditions, the observed resistance was comparable to the protection obtained by commercially available IR stimuli or nematicides. Via mRNA sequencing and confirmatory biochemical assays, it was proven that mCOPE-IR in rice is associated with systemic effects on ethylene accumulation, reactive oxygen species (ROS) metabolism and cell wall-related modifications. While no negative trade-offs were detected with respect to plant growth or plant susceptibility to necrotrophic pests or pathogens, additional infection experiments indicated that mCOPE may have a predominant activity toward biotrophs. In summary, the presented data illustrate a propitious potential for these extracts, which can be derived from agro-industrial waste streams.

Abstract 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.

Biochar has been reported to play a positive role in disease suppression against airborne pathogens in plants. The mechanisms behind this positive trait are not well-understood. In this study, we hypothesized that the attraction of plant growth-promoting rhizobacteria (PGPR) or fungi (PGPF) underlies the mechanism of biochar in plant protection. The attraction of PGPR and PGPF may either activate the innate immune system of plants or help the plants with nutrient uptake. We studied the effect of biochar in peat substrate (PS) on the susceptibility of strawberry, both on leaves and fruits, against the airborne fungal pathogen Botrytis cinerea. Biochar had a positive impact on the resistance of strawberry fruits but not the plant leaves. On leaves, the infection was more severe compared with plants without biochar in the PS. The different effects on fruits and plant leaves may indicate a trade-off between plant parts. Future studies should focus on monitoring gene expression and metabolites of strawberry fruits to investigate this potential trade-off effect. A change in the microbial community in the rhizosphere was also observed, with increased fungal diversity and higher abundances of amplicon sequence variants classified into Granulicella, Mucilaginibacter, and Byssochlamys surrounding the plant root, where the latter two were reported as biocontrol agents. The change in the microbial community was not correlated with a change in nutrient uptake by the plant in either the leaves or the fruits. A decrease in the defense gene expression in the leaves was observed. In conclusion, the decreased infection of B. cinerea in strawberry fruits mediated by the addition of biochar in the PS is most likely regulated by the changes in the microbial community.

Abstract 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.

Abstract 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 Pochazia 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.

Three characteristics are considered key for optimal use of composts in growing media: maturity, pH and organic matter content. Maturation is a critical step in the processing of composts contributing to compost quality. Blending of composts with chopped heath biomass, sieving out the larger fraction of composts and acidification of composts by adding elemental sulfur may be used either to increase organic matter content or to reduce pH for a better fit in growing media. While several studies have shown the effectiveness of these treatments to improve the use of composts in growing media, the effect of these treatments on the compost microbiome has merely been assessed before. In the present study, five immature composts were allowed to mature, and were subsequently acidified, blended or sieved. Bacterial and fungal communities of the composts were characterized and quantified using 16S rRNA and ITS2 gene metabarcoding and phospholipid fatty acid analysis. Metabolic biodiversity and activity were analyzed using Biolog EcoPlates. Compost batch was shown to be more important than maturation or optimization treatments to determine the compost microbiome. Compost maturation increased microbial diversity and favored beneficial microorganisms, which may be positive for the use of composts in growing media. Blending of composts increased microbial diversity, metabolic diversity, and metabolic activity, which may have a positive effect in growing media. Blending may be used to modify the microbiome to a certain degree in order to optimize microbiological characteristics. Acidification caused a decrease in bacterial diversity and microbial activity, which may be negative for the use in growing media, although the changes are limited. Sieving had limited effect on the microbiome of composts. Because of the limited effect on the microbiome, sieving of composts may be used flexible to improve (bio)chemical characteristics. This is the first study to assess the effects of maturation and optimization treatments to either increase organic matter content or lower pH in composts on the compost microbiome.

Abstract 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.

Abstract 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.

Abstract 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 mycotoxin deoxynivalenol (DON), produced in wheat, barley and maize by Fusarium graminearum and Fusarium culmorum, is threatening the health of humans and animals. With its worldwide high incidence in food and feed, mitigation strategies are needed to detoxify DON, maintaining the nutritional value and palatability of decontaminated commodities. A promising technique is biological degradation, where microorganisms are used to biotransform mycotoxins into less toxic metabolites. In this study, bacterial enrichment cultures were screened for their DON detoxification potential, where DON and its potential derivatives were monitored. The residual phytotoxicity was determined through a bioassay using the aquatic plant Lemna minor L. Two bacterial enrichment cultures were found to biotransform DON into a still highly toxic metabolite for plants. Furthermore, a cytotoxic effect was observed on the cellular viability of intestinal porcine epithelial cells. Through liquid chromatography high-resolution mass spectrometry analysis, an unknown compound was detected, and tentatively characterized with a molecular weight of 30.0 Da (i.e., CH2O) higher than DON. Metabarcoding of the subsequently enriched bacterial communities revealed a shift towards the genera Sphingopyxis, Pseudoxanthomonas, Ochrobactrum and Pseudarthrobacter. This work describes the discovery of a novel bacterial DON-derived metabolite, toxic to plant and porcine cells.

Biochar has previously been used in growing media blends as fertilizer or for improving plant growth, disease suppression, and as a sustainable replacement of peat. To achieve optimal circular horticulture, we propose here to reuse the biochar from spent growing media. However, it is unclear to what extent the biochar feedstock determines the mode of action of the biochar and if use of spent growing media biochar may encounter nutrient or salt problems. Differences in chemical characteristics, nutrient release, and interaction in a leaching experiment and effects on plant growth, nutrient uptake, and disease suppression in a strawberry greenhouse trial were studied for 11 biochars either processed from spent growing media or from lignocellulosic biomass. A well-studied biochar produced from oak wood was set as reference. Biochars produced from spent growing media were characterized by higher electrical conductivity, extractable and total nutrient concentrations compared with biochars produced from lignocellulosic biomass. Especially in the first phase of the leaching experiment, all biochars showed nutrient and salt release, with most prominent effects for spent growing media biochars and the reference biochar. The latter biochars were an important source of phosphorus and in particular of potassium. Only for the reference biochar, strawberry plants showed increased uptake of phosphorus, potassium and calcium, and increased chlorophyll concentration. No Bortrytis cinerea disease suppression and no increase in plant growth was observed for the tested biochars. It is concluded that spent growing media can be recycled as biochar in growing media without adverse effects compared to biochars produced from lignocellulosic biomass.

Peat based growing media are not ecologically sustainable and often fail to support biological control. Miscanthus straw was (1) tested to partially replace peat; and (2) pre-colonized with a Trichoderma strain to increase the biological control capacity of the growing media. In two strawberry pot trials (denoted as experiment I & II), extruded and non-extruded miscanthus straw, with or without pre-colonization with T. harzianum T22, was used to partially (20% v/v) replace peat. We tested the performance of each mixture by monitoring strawberry plant development, nutrient content in the leaves and growing media, sensitivity of the fruit to the fungal pathogen Botrytis cinerea, rhizosphere community and strawberry defense responses. N immobilization by miscanthus straw reduced strawberry growth and yield in experiment II but not in I. The pre-colonization of the straw with Trichoderma increased the post-harvest disease suppressiveness against B. cinerea and changed the rhizosphere fungal microbiome in both experiments. In addition, defense-related genes were induced in experiment II. The use of miscanthus straw in growing media will reduce the demand for peat and close resource loops. Successful pre-colonization of this straw with biological control fungi will optimize crop cultivation, requiring fewer pesticide applications, which will benefit the environment and human health.