Unusual features of pomoviral RNA movement

This work is partially supported by the Scottish Government’s Rural and Environment Science and Analytical Services (RESAS) DivisionPotato mop-top pomovirus (PMTV) is one of a few viruses that can move systemically in plants in the absence of the capsid protein (CP). Pomoviruses encode the triple gene block genetic module of movement proteins (TGB 1, 2, and 3) and recent research suggests that PMTV RNA is transported either as ribonucleoprotein (RNP) complexes containing TGB1 or encapsidated in virions containing TGB1. Furthermore, there are different requirements for local or systemic (long-distance) movement. Research suggests that nucleolar passage of TGB1 may be important for the long-distance movement of both RNP and virions. Moreover, and uniquely, the long-distance movement of the CP-encoding RNA requires expression of both major and minor CP subunits and is inhibited when only the major CP sub unit is expressed. This paper reviews pomovirus research and presents a current model for RNA movement.Publisher PDFPeer reviewe

Bacterial endophytome sources, profile and dynamics—a conceptual framework

Currently, it seems inconceivable to dispute the major role of microorganisms in human health or insects with endosymbionts. Although microbial endophytes were discovered long ago, little is known about the roles of plant-associated microorganisms. Some endophytes are horizontally transmitted, whereas others are seed-borne; together, they influence plant health. Beneficial endophytes can promote plant growth and yield by increasing plant resistance to biotic and abiotic stresses. Recently, the tools available to study the phytobiome have much improved, opening doors for a better understanding of the fascinating interactions taking place at the plant level. This review redefines the conceptual framework for “endophyte” and “endophytome,” focusing on the intricate dynamics of bacterial endophytomes. Systematically examining the formation pathways and profiling endophytes allows for a comprehensive exploration of the intricate dynamics governing plant-microbe interactions. Additionally, the assessment of how endophytomes are influenced by both biotic and abiotic factors provides essential insights into the adaptability and resilience of plant-associated microorganisms. Our comprehensive analysis integrates genomic insights with environmental considerations, offering a nuanced perspective on the functional roles of bacterial endophytomes. Therefore, a new, inclusive definition is essential to accurately represent the complexity of interactions within the plant microbiome as well as having the whole picture of associated concepts

Variation in the transmission of barley yellow dwarf virus-PAV bydifferent Sitobion avenae clones in China

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Scientific Opinion on the pest categorisation of Strawberry vein banding virus

The Panel on Plant Health performed a pest categorisation of Strawberry vein banding virus (SVBV) for the European Union (EU) territory. SVBV is a well-defined virus species of the genus Caulimovirus for which the entire genome sequence is known and molecular detection assays are available. SVBV is transmitted by vegetative multiplication of infected hosts and through the activity of aphid vectors, the most efficient being Chaetosiphon spp. The virus is reported from all continents and is present in three EU Member States: the Czech Republic, Italy and Slovakia. The host range of SVBV is restricted to cultivated and wild strawberries. It is listed in Annex IAI of Directive 2000/29/EC. SVBV is not expected to be affected by ecoclimatic conditions wherever its hosts are present and has the potential to establish in large parts of the EU territory, and to subsequently spread through the action of its Chaetosiphon fragaefolii vector, which is present in many Member States. SVBV does not cause severe symptoms, and modern cultivars are mostly symptomless if infected with SVBV alone. SVBV can, however, contribute to more severe symptoms when it occurs in mixed infections with other strawberry viruses. Despite this, SVBV is considered a minor problem in strawberry production as a consequence of modern practices including the systematic use of certified planting materials and the use of short crop cycles, which have greatly reduced the impact of strawberry viruses. Overall, SVBV does not have the potential to be a quarantine pest as, given current agricultural practices, it does not fulfil the pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 11 of having a severe impact. However, SVBV has the potential to be a regulated non-quarantine pest because it fulfils all pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 21

Scientific Opinion on the pest categorisation of Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley [syn. Phoma tracheiphila (Petri) L.A. Kantschaveli & Gikashvili]

The European Commission requested the EFSA Panel on Plant Health to perform a pest categorisation of Phoma tracheiphila, the fungal pathogen responsible for “mal secco” disease of citrus. This pathogen is listed in Annex IIAII of Directive 2000/29/EC. Recently, the pathogen has been reclassified as Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley, based on molecular phylogenetic analysis. Plenodomus tracheiphilus is a single taxonomic entity, and sensitive and specific methods are available for its differentiation from other related Plenodomus species. The main host is lemon (Citrus limon L.), but the pathogen has also been reported on other species of the genera Citrus, Fortunella, Poncirus and Severinia and on their hybrids. Host plants are widely grown in the southern EU Member States (MSs) and climatic conditions are conducive to disease development in both orchards and nurseries. The pathogen is present in part of the risk assessment area, being mainly reported on lemon grown in Italy, Greece, Cyprus and France, where it has a serious impact on the citrus industry. There are no obvious ecological/climatic factors limiting the potential establishment and spread of the pathogen in the, so far, non-infested citrus-producing EU MSs (i.e. Spain, Portugal, Malta and Croatia). Short-distance spread of the pathogen occurs via water splash and wind-driven rain, whereas movement of infected host plants for planting, particularly asymptomatic plants, is considered to be responsible for the introduction of the pathogen into new areas. Cultural practices and copper-based fungicide sprays may reduce inoculum sources and prevent new infections but they cannot eliminate the pathogen. P. tracheiphilus fulfils all of the pest categorisation criteria for having the potential to be a quarantine pest and a regulated non-quarantine pest, as those are defined in the International Standards for Phytosanitary Measures No 11 and 21, respectively

Scientific Opinion on the pest categorisation of Beet leaf curl virus

The Panel on Plant Health performed a pest categorisation of Beet leaf curl virus (BLCV) for the European Union (EU) territory. BLCV mainly infects Beta spp., as well as Spinacia spp., Tetragonia tetragonioides and the common weeds Atriplex spp. and Chenopodium spp. This putative Rhabdovirus is not a recognised virus species; it is only defined by particle morphology and by its circular propagative transmission by the lace bug Piesma quadratum. No efficient diagnostic assay is available for BLCV, which was reported in only Germany and Turkey. With a few exceptions, there is no record of BLCV after 1983. BLCV is listed in Annex IIAII of Directive 2000/29/EC. The virus itself is not expected to be affected by ecoclimatic conditions and its P. quadratum vector is widely distributed in the EU; thus, BLCV has the potential to establish and spread over large areas of the EU and cause significant damage in sugarbeet. However, it appears to have caused sporadic outbreaks in only some years, possibly associated with high vector populations. It does not appear to have had any significant impact in recent years, and it may now no longer be significantly present in agricultural production systems. This situation is possibly a consequence of current intensive sugarbeet crop management practices and of the ensuing reduction in vector populations. Owing to the very limited literature available on BLCV, a full pest risk assessment is highly unlikely to provide clearer insight into the risks associated with this virus than the present pest categorisation

On the use of antibiotics to control plant pathogenic bacteria: a genetic and genomic perspective

Despite growing attention, antibiotics (such as streptomycin, oxytetracycline or kasugamycin) are still used worldwide for the control of major bacterial plant diseases. This raises concerns on their potential, yet unknown impact on antibiotic and multidrug resistances and the spread of their genetic determinants among bacterial pathogens. Antibiotic resistance genes (ARGs) have been identified in plant pathogenic bacteria (PPB), with streptomycin resistance genes being the most commonly reported. Therefore, the contribution of mobile genetic elements (MGEs) to their spread among PPB, as well as their ability to transfer to other bacteria, need to be further explored. The only well-documented example of ARGs vector in PPB, Tn5393 and its highly similar variants (carrying streptomycin resistance genes), is concerning because of its presence outside PPB, in Salmonella enterica and Klebsiella pneumoniae, two major human pathogens. Although its structure among PPB is still relatively simple, in human- and animal-associated bacteria, Tn5393 has evolved into complex associations with other MGEs and ARGs. This review sheds light on ARGs and MGEs associated with PPB, but also investigates the potential role of antibiotic use in resistance selection in plant-associated bacteria