In a study of diseases caused by Xanthomonas campestris on UK nursery-grown wallflowers (Erysimum cheiri), one isolate (P764) obtained in 1990 from Sussex differed from the others. The affected plants (cv. Bedder Mixed), showed distorted growth with chlorotic and necrotic spots, but no sectored V-shaped wilting, the most common symptom associated with xanthomonads in wallflowers. Other X. campestris isolates (including P763), were obtained from wallflowers with typical wilting. Infected plant material was comminuted in sterile 0.1% peptone solution and loopfuls streaked onto yeast dextrose chalk agar and nutrient dextrose agar (Lelliott & Stead, 1987). Plates were incubated for up to 72 hours at 28°C. Xanthomonas-like colonies were purified by re-streaking and isolates were maintained at -80°C (Protect System, UK).

In a study of diseases caused by Xanthomonas campestris on UK nursery-grown wallflowers ( Erysimum cheiri ), one isolate (P764) obtained in 1990 from Sussex differed from the others. The affected plants (cv. Bedder Mixed), showed distorted…

The International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria has responsibility to evaluate the names of newly proposed pathovars for adherence to the International Standards for Naming Pathovars of Phytopathogenic Bacteria. Currently, the Comprehensive List of Names and the List of New Names of Plant Pathogenic Bacteria provide the authoritative register of names of bacterial plant pathogens. In this manuscript we up-date the list of names by cataloguing and evaluating names of plant pathogenic bacteria published in 2011 and 2012. We provide those names that have been validly and effectively published in this time frame, the proposed names that we judged to be invalid, and names published earlier that did not make the previous lists.

In 2010 the International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria published the Comprehensive List of Names of Plant Pathogenic Bacteria, 1980-2007 to provide an authoritative register of names of plant pathogens. In this manuscript we update the list of names by cataloguing names published from 2008 to 2010. We provide those names that have been validly and effectively published in this time frame, the proposed names that we judged to be invalid and names published earlier that did not make the previous lists. We also discuss problems that arise in the naming of strains that fall into the status Candidatus and nomenclatural problems in the genus Xanthomonas.

In 2010 the International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria published the Comprehensive List of Names of Plant Pathogenic Bacteria, 1980-2007 to provide an authoritative register of names of plant pathogens. In this manuscript we update the list of names by cataloguing names published from 2008 to 2010. We provide those names that have been validly and effectively published in this time frame, the proposed names that we judged to be invalid and names published earlier that did not make the previous lists. We also discuss problems that arise in the naming of strains that fall into the status Candidatus and nomenclatural problems in the genus Xanthomonas.

Survival of Ralstonia solanacearum race 3 biovar 2 (phylotype II sequevar 1) in Egyptian soils and compost was studied under laboratory and field conditions. Survival of the pathogen under laboratory conditions varied with temperature, water potential and soil type, with temperature being the major determinant of survival of the pathogen. The effects of temperature and moisture content were variable between different experiments, but survival was generally longer at 15°C than at 4, 28 and 35°C respectively. Survival was also longer when moisture levels were constant compared with varying moisture levels at all temperatures. In experiments to compare the effects of progressive drying in sandy and clay soils there was a difference in survival times between the two soil types. In sandy soils, the pathogen died out more rapidly when soil was allowed to dry out than in controls where the soil was kept at constant water potential. In clay soils there was little difference between the two treatments, possibly due to the formation of a hard impermeable outer layer during the drying process, which retarded water loss from within. Survival in mature composts at 15°C was of the same order of magnitude as in soils but shorter at 28°C, possibly owing to increased biological activity at this temperature, or a resumption of the composting process, with concomitant higher temperatures within the compost itself. The maximum survival time recorded over all soil types and conditions during in vitro studies was around 200 days. In field studies, the maximum survival time in both bare sand and clay was around 85 days at depths up to 50 cm. The survival time was reduced in field experiments carried out in summer to less than 40 days and in one study when the ground was flooded for rice cultivation, the bacterium could not be detected 14 days after flooding. The maximum survival time of R. solanacearum in infected plant material or in infested soil samples incorporated into compost heaps was less than 2 weeks. At the culmination of field soil and compost experiments, no infection was detected in tomato seedlings up to 10 weeks after transplanting into the same soils or composts under glasshouse conditions at a temperature of 25°C.

The reclassification of Erwinia chrysanthemi into six new Dickeya species (Samson et al., 2005) has resulted in the need to confirm identities of the strains held in the National Collection of Plant Pathogenic Bacteria (NCPPB). This process is being done using fatty acid profiling, repetitive sequence PCR and phylogenetic identification based on several partial gene sequences, but primarily the recA gene. Prior to the proposal for Dickeya spp., E. chrysanthemi was classified both by a pathovar system based on host specificity (Bradbury, 1986) and biovar systems based on nutritional and physiological differences. The most widely used biovar system was that of Ngwira & Samson (1990) and Samson et al. (1990). Correlation between the systems was not good. TwoE.chrysanthemi strains isolated fromwilting florist chrysanthemum plants (Chrysanthemum morifolium cv. Mayford’s Perfection) in different nurseries in Bedfordshire and Hertfordshire in 1970 were acceded to the NCPPB as E. chrysanthemi pv. chrysanthemi (NCPPB 2339 and NCPPB 2340).FattyacidprofilingusingtheMIDIsystem,showedthatthesestrains did not cluster with other E. chrysanthemi pv. chrysanthemi strains including the pathotype reference strain NCPPB 402. Nutritional tests used todifferentiate thebiovarsofE.chrysanthemigaveatypical results for biovar 5, regarded as being synonymous with E. chrysanthemi pv. chrysanthemi (Ngwira & Samson 1990, Samson et al., 1990), but had similarities to biovar 3. Biovar 3 strains have been reclassified largely into DickeyazeaeandDickeyadadantii (Samsonetal., 2005). A phylogeny based on a 481 bp sequence of the recA gene, placed NCPPB 2339 and 2340 in the same phylogenetic clade as the type strain of D. zeae (NCPPB 2538) and all other maize strains (n 1⁄4 19) tested from the NCPPB. This result is supported by fatty acid profiling and repetitive sequence PCR, using REP and ERIC primers, of all Dickeya species type strains. Both strains clustered exclusively with D. zeae strains in UPGMA dendrograms for all three assays. These results clearly show that these two strains do not belong to D. chrysanthemi bv. chrysanthemi (Samson et al., 2005) but are typical members of D. zeae. NCPPB 2339 was included in the study of Samson et al. (2005) and shown to be D. zeae but was wrongly quoted as being from the USA. Thus, examination of archival strains using current taxonomic methods has demonstrated that these are the first and currently the only records of D. zeae causing plant disease in the UK. This also highlights the importance of applying up-to-date identification methods to avoid overlooking significant new findings.

The names of all plant pathogenic bacteria which have been effectively and validly published in terms of the international. Code of Nomenclature of Bacteria and the Standards for Naming Pathovars are listed to provide an authoritative register of names for use by authors, journal editors and others who require access to currently correct nomenclature. Included are species, subspecies and pathovar names and details of type and pathotype strains reported from 1980 to 2007. An explanation of how to use this list is provided. In recent years the taxonomy of plant pathogenic bacteria has been extensively revised. For some taxa there are several valid synonyms. Unless otherwise stated, the most recently published name is used in this list as the reference name (in bold italic) to which all other synonyms are referred. This does not mean that the reference name is always to be preferred. A synonym, i.e., a previously published name for the same organism, may represent a classification considered by individual scientists or groups to give a more coherent taxonomy and may be used. This list is presented by the International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria, Carolee T. Bull Convener.

A unified approach to naming bacteria ensures accurate communication among scientists, regulators and the public. Rules for nomenclature, set out in the International Code of Nomenclature of Bacteria (ICNB), ensure that proposals for new names and combinations follow a logical and standardized progression that maintains the integrity of the established nomenclature while facilitating changes based on scientific inquiry into relationships among organisms. However, these Rules only apply to ranks at the level of subspecies and above and not to lower taxonomic ranks. The pathovar is one infraspecific rank that is widely used in the classification and nomenclature of plant pathogenic bacteria and is often included in legislation to provide statutory control of bacterial plant pathogens. Thus, phytobacteriologists must rely on two discontinuous but, complimentary systems: the Rules set forth in ICNB for naming down to subspecies level, and the Standards in the International Standards for Naming Pathovars of Plant Pathogenic Bacteria to name pathovars. A framework for determining the priority of names is provided by the Approved Lists of Bacterial Names, which gives genus, species and subspecies names and their corresponding type strains, and subsequent lists of validly published names appearing in the International Journal of Systematic and Evolutionary Microbiology. For pathovar names priority is based on the date of valid publication of legitimate names. A list of pathovar names and pathotype strains is maintained by the Committee on the Taxonomy of Plant Pathogenic Bacteria of the International Society of Plant Pathology. To help researchers avoid common pitfalls encountered when developing nomenclature for novel classification systems, this manuscript clarifies several key Rules and Standards. It aims to promote best practice, in that names developed to conform to the ICNB should also consider precedents set by previous nomenclatural designations as per the International Standards for Naming Pathovars of Plant Pathogenic Bacteria, thus ensuring continuity across the nomenclature of all phytopathogenic bacteria.

Comparative analyses were undertaken to characterize Xanthomonas campestris pv. musacearum, the causal agent of a wilt of enset and banana, and to assess its relatedness to other xanthomonads by fatty acid methyl esters, genomic fingerprinting using rep‐PCR and partial nucleotide sequencing of the gyrase B gene. The results from all three analyses indicated that strains of X. campestris pv. musacearum are homogeneous and very similar to X. vasicola strains isolated from sugarcane and maize from Africa. Pathogenicity studies indicated that strains of X. vasicola pv. holcicola and X. vasicola from sugarcane induced no symptoms on banana, whereas X. campestris pv. musacearum produced severe disease. These data will support a future proposed reclassification of X. campestris pv. musacearum as X. vasicola pv. musacearum when more data are available.

Various Pseudomonas syringae pathovars cause leaf spots and cankers of hardy nursery stock species in the UK, including P.s. pv. syringae on lilac, P.s. pv. berberidis on Berberis spp. and P.s. pv. philadelphi on Philadelphus spp. (Roberts, 1997). Leaf spots on some other hosts are attributed to P.s. pv. syringae or to P. syringae pv. undetermined. Occasionally Central Science Laboratory has received samples of Viburnum spp. with watersoaked leaf spots from which P. syringae has been isolated; one was from Viburnum tinus in 1986. The isolate, a typical LOPAT group 1 member of P. syringae (Lelliott & Stead, 1987), was placed in the National Collection of Plant Pathogenic Bacteria (NCPPB) as NCPPB 3450 and was listed under P.s. pv. viburni with a ‘b’ ranking, denoting authenticity not verified. More recently, plants of Viburnum sargentii with typical bacterial leaf spots were received from a Lincolnshire nursery and from which LOPAT 1 strains were isolated. Host tests confirmed pathogenicity on Viburnum sargentii but it was weaker on Viburnum opulus var. Sterile. Two isolates from V. sargentii on the same nursery, taken at different times (CSL 4205 and 4206), were acceded to the NCPPB as NCPPB 4265 and NCPPB 4266, respectively. Fatty acid profiles obtained were typical of P. syringae. REP-PCR based on primers from the repetitive enterobacterial consensus sequence and BOX-PCR, based on primers from the BOX A subunit, were carried out (Stead et al., 2000). Fingerprints were compared with those of reference strains of all validly named P. syringae pathovars held in the NCPPB, including P.s. pv. viburni (NCPPB 1921, the only authentic strain). upgma dendrograms of both assays showed that NCPPB 3450 did not have the profile of P.s. pv. viburni but was very similar to that of P.s. pv. maculicola and P.s. pv. tomato. However, NCPPB 4265 and NCPPB 4266 had profiles very similar to that of the P.s. pv. viburni type strain and were different from all other reference strains. Bradbury (1986) lists the known distribution as USA and Spain, with the Spanish strains coming from a rot of tobacco. This is the first authentic record of P.s. pv. viburni in the UK. The precise taxonomic position of NCPPB 3450 remains uncertain. This work was funded by DEFRA Plant Health Division Project PH0154.

During a serious epidemic of crown and cane gall on the blackberry-raspberry (Rubus occidentalis-Rubus idaeus) hybrid Lockness in a specialized crop in the province of Treviso (northern Italy) Gram-negative bacteria were found associated with tumours. Following experimental inoculation these bacteria caused tumours on tomato stems and on pot-grown hybrid canes in the greenhouse. These bacteria were found to possess a Ti plasmid, common to Agrobacterium. The resulting fatty acid profile did not correspond to any known Agrobacterium species, but did indicate an affinity with the genus Agrobacterium. Partial 16S rRNA sequencing revealed that the bacteria were closely related to three strains of Agrobacterium rhizogenes, in particular with a strain isolated from a peach tumour.

Avirulent pathogenic bacteria often cause a hypersensitive response (HR) in plants, an effective resistance phenomenon coupled to programmed cell death (PCD) and usually an increased production of reactive oxygen species (ROS) in the infected cells. HR induction is dependent on Ca2+ accumulation/influx within the plant cytoplasm. Here we show that Lanthanum (La3+), a Ca2+ channel blocker, inhibited PCD and H2O2 accumulation in tobacco leaf tissue injected with Pseudomonas savastanoi pv. phaseolicola, an avirulent pathogen, even if it was added up to 4.5 h after the bacterium. This was 2 h after the HR induction phase and the beginning of an intense ROS accumulation in the control (HR-positive) leaf tissue. However, La3+ did not inhibit transcription of the pathogenesis-related protein PR-la gene and only partially blocked the HR-associated resistance. We conclude that during HR: 1) Ca2+ influx is needed not only to trigger but also to maintain ROS production and processes leading to PCD; 2) There is a PCD- and ROS-independent resistance mechanism. The comparison of this "remaining" resistance with the early induced resistance (EIR) needs further analysis.

Growth chamber experiments showed that acibenzolar-S-methyl (ASM) (50divided by50 muM) treatments systemically protect tomato plants against Pseudomonas syringae pv. tomato. Evidence for this was the reduction in bacterial spot diameter and bacterial growth in planta. The efficacy of ASM was also found in open field conditions, where both leaves and fruit were protected from the disease. The best efficacy (about 80%) was obtained by spraying the plants 6divided by8 times with a mixture of ASM and copper hydroxide (2.5 + 80 g hl(-1) active ingredient). Open field experiments revealed that neither quality nor quantity of fruit yield were negatively affected by ASM treatments. By using the HPLC method of Scarponi et al. (2001), we showed that ASM rapidly translocates from treated to untreated tomato leaves, with the maximum translocation occurring 8 h after the treatment. ASM residues decreased as the time elapsed in both treated and untreated tomato leaves, reaching negligible values 72 h after treatment. We also demonstrated that the acidic derivative of ASM (CGA 210007), which systemically protected tomato plants against P. s. pv. tomato, was formed in tomato plants as early as 2 h after ASM treatment, albeit only in the treated leaves. CGA 210007 residues decreased in treated tomato leaves with a trend similar to that observed for ASM. Since neither ASM nor CGA 210007 inhibited bacterial growth in vitro and the protection against bacterial speck of tomato has been observed after the two compounds were completely degraded, we can conclude that the protection must be due to the activation of the plant's defence mechanisms.

Lipodepsipeptides (LPDs) are a group of cyclic, acylated peptides produced by several Pseudomonas species. They are usually divided in two groups, mycins and peptins, on the basis of the size of the amino acidic part of the molecule. Mycins have a ring of 9 amino acids closed between the first and the last residue, peptins contain a more complex peptide moiety of up to 25 amino acids, partially cyclized. Both mycins and peptins attack the plasma membrane, but may have different target organisms. Comparing the mode of action of these two classes of LDPs on natural and model membranes we observed that all peptides induced red blood cell haemolysis and leakage of tonoplasts and liposornes by the formation of pores. The haemolytic activity of the smaller mycins was higher than that of the bigger peptins and proportional to the amphipathic index of the molecule. The extent of permeabilization was dependent also on the composition of the lipid membrane. In particular, mycins show a preference for sterols, whereas peptins are more active on phospholipids, especially sphingomyelin. These differences may have physiological implications. The formation of discrete ion channels, with anionic selectivity, was directly demonstrated by electrophysiological experiments performed on planar lipid bilayers or sugar beet vacuoles. The channels show sub-states and their properties in vacuoles and in planar lipid membranes were remarkably similar.

Significantly higher levels of bacterial streak and bulb rot of onion (BSBR), caused by Pseudomonas viridiflava, occurred in onions receiving excessive applications of fertiliser and were correlated with higher nitrogen content in plant tissues. Based on previous work that weeds, particularly cutleaf evening primrose (Oenothera laciniata), were the primary source of initial inoculum, oxyfluorfen was evaluated as a post-emergence herbicide after transplanting. The herbicide not only reduced weed levels as expected, but also reduced the incidence of BSBR. Lower levels of BSBR also occurred in plots treated with weekly applications of cupric hydroxide and maneb when compared to non sprayed plots, or plots treated only with the fungicide chlorothalonil. Harvesting onions with cutting shears contaminated with P. viridiflava increased the incidence of postharvest rots in onions clipped immediately after uprooting but not in onions allowed to cure in the field for 48 h. Finally, lower levels of postharvest disease occurred when onion bulbs were stored under controlled-atmospheric (CA) conditions (3% oxygen, 5% carbon dioxide, and 92% nitrogen) at 1degreesC. The various control procedures were combined into an integrated management strategy for the control of BSBR in Georgia.

Recent developments in the taxonomy and nomenclature of Pseudomonas syringae pathovars are reviewed and a consensus classification within the species is outlined. Proposals for some conservative nomenclatural changes are discussed.

Many micro-organisms including pathogenic and saprophytic bacteria react with plant cells in the intercellular spaces inducing different defence responses. The local Early Induced Resistance (EIR) is a first line defence mechanism against bacteria. Here an overview will be given of this local, nonspecific, symptomless defence mechanism as a separate entity from the incompatible-specific Hypersensitive Response (HR). The EIR operates 1-6 h after inoculation (hpi) for about one day depending on temperature and leaf age. The EIR can be inhibited by a short heat shock (50degreesC for 15 sec) of leaves or by a plant protein synthesis inhibitor, cycloheximide (5 mug ml(-1)). In a compatible host-pathogen relationship (Pseudomonas syringae pv. tabaci/tobacco) the effect of EIR does not eventuate. However, the EIR develops simultaneously with the HR and sometimes is able to prevent it when the induction time of HR is longer than the time required for the development of the EIR (e.g. P. s. pv. phaseolicola does not induce HR in tobacco above 28degreesC). It seems that the EIR inhibits the metabolism of bacteria and the activity of hrp genes. Moreover, EIR activates the accumulation of H2O2 at the bacterial attachment site expressing new peroxidase isoenzymes in the initiated plant tissue. Further investigations, hopefully, will clarify the relationship of other complementary defence mechanisms like local late induced resistance (LIR) examined by Sequeira (1983) and Mazzucchi and co-workers (1979), Minardi (1995), Newman et al., (2001).