Monitoring the occurrence of tomato bacterial spot and range of the causal agent Xanthomonas perforans in Iran

A 2‐year comprehensive field survey was conducted across major tomato‐growing areas of Iran. Two hundred and thirty‐four tomato fields and six tomato‐producing greenhouses were surveyed for the potential presence of bacterial spot disease. Five hundred and ninety‐six tomato samples with and without symptoms were analysed. While Xanthomonas spp. were found in association with tomato plants both with and without symptoms from five surveyed counties, the bacterial spot disease was observed only in plants from three of them. Only strains isolated from plants with symptoms induced disease symptoms on tomato, while those isolated from symptomless plants caused symptoms only on cabbage and common bean. None of the isolates caused disease symptoms on pepper and eggplant. Phylogenetic analysis showed that X. perforans is the causal agent of tomato bacterial spot in Iran, although X. campestris and X. axonopodis were also associated with symptomless tomato plants. All X. perforans isolates in this study were sensitive to streptomycin, copper sulphate and copper oxychloride at concentrations of 50 mg L^?1, 200 mg L^?1 and 0.8 g L^?1, respectively. Unlike the type strain of X. perforans, isolates in this study did not produce bacteriocin against other Xanthomonas spp., nor were they detected using the usual species‐specific primer pair Bs‐XpF/Bs‐XpR. This suggests an atypical nature of X. perforans strains in Iran, which leads to the hypothesis that X. perforans strains in Iran may have a separate origin to those causing disease epidemics elsewhere. The aggregated dispersal pattern of the diseased tomato fields signifies the seedborne introduction of the pathogen into the country.     

Characterization and PCR-based Typing of Xanthomonas campestris pv. vesicatoria from Peppers and Tomatoes in Serbia

During the last two decades bacterial strains associated with necrotic leaf spots of pepper and tomato fruit spots were collected in Serbia. Twenty-eight strains isolated from pepper and six from tomato were characterized. A study of their physiological and pathological characteristics, and fatty acid composition analysis revealed that all of the strains belong to Xanthomonas campestris pv. vesicatoria. Being non-amylolytic and non-pectolytic, pathogenic on pepper but not on tomato, containing lower amounts of fatty acid 15 : 0 ante–iso, the pepper strains were designated as members of the A group of X. campestris pv. vesicatoria. However, the tomato strains hydrolyzed starch and pectate, caused compatible reactions on tomato but not on pepper, had higher percent of 15 : 0 ante–iso fatty acid, and were classified into B phenotypic group and identified as X. vesicatoria. PCR primers were developed which amplified conserved DNA regions related to the hrp genes of different strains of X. campestris pv. vesicatoria associated with pepper and tomato. Restriction analysis of the PCR product resulted in different patterns and enabled grouping of the strains into four groups. When xanthomonads isolated from pepper and tomato in Serbia were analyzed, they clustered into two groups corresponding to the grouping based on their physiological and pathological characteristics. According to the reaction of pepper and tomato differential varieties, the strains from pepper belong to races P7 and P8 and tomato strains belong to the race T2. All strains were sensitive to copper and streptomycin. Advantages and disadvantages of various bacterial spot management practices are discussed.     

Widespread distribution of Xanthomonas perforans and limited presence of X. gardneri in Brazil

Tomato bacterial spot is caused by Xanthomonas euvesicatoria, X. vesicatoria, X. perforans and X. gardneri. In order to determine the distribution, frequency of occurrence, and diversity of these species in the Brazilian commercial tomato fields, a survey was conducted between 2009 and 2012. In this period, 204 strains were obtained from 33 counties (22 with processing tomatoes and 11 with fresh‐market tomatoes). Pathogenicity tests, BOX‐PCR, PCR with species‐specific primers, and sequence analysis of the avirulence gene avrXv3 were performed in order to identify the strains at species and race level. Xanthomonas perforans predominated among the strains (92%) and was present in most counties. In addition, this species was prevalent in most areas of both fresh‐market tomatoes (63.6% of counties surveyed) and processing tomatoes (95.4% of counties surveyed). Fifteen strains (7.5%) were identified as X. gardneri, which was found mostly in fresh‐market fields located at regions with altitude higher than 900 m, and only one strain of X. euvesicatoria (0.5%) was found in a processing tomato field. High genetic diversity was observed within X. perforans, with 137 BOX‐PCR haplotypes. Race T3 prevailed (97.5%), but reported here for the first time is the occurrence of five strains identified as race T4 in fresh‐market fields in the state of São Paulo. The race T4 phenotype of these strains resulted from the presence of an 859 bp insertion in the avirulence gene avrXv3. This insertion is related to amino acid sequences of a transposase found in X. gardneri, and to amino acid sequences of X. campestris.     

Pathogenicity and virulence gene content of Xanthomonas strains infecting Araceae,formerly known as Xanthomonas axonopodis pv. dieffenbachiae

Bacterial leaf blight of aroids is caused by a heterogeneous group of xanthomonads listed as Xanthomonas axonopodis pv. dieffenbachiae (Xad) on the EPPO A2 quarantine list. Recently, Xad strains were shown not to belong to X. axonopodis but to the species X. citri, X. phaseoli and X. euvesicatoria. Here, to verify the pathovar designation, 11 representative strains were tested for pathogenicity on six aroid genera. They had overlapping host ranges and only the strain isolated from Syngonium showed host specificity. The X. citri strains, isolated from various hosts, showed dissimilarity in virulence to the tested aroid genera. The X. phaseoli strains, isolated from Anthurium and Syngonium, were generally more virulent and, additionally, induced systemic infections. The X. euvesicatoria strains, isolated from Philodendron, were scored as not pathogenic on the tested aroids. Four representative strains were genome sequenced and showed a variable virulence‐associated gene content. Pathogenicity to aroids was correlated with the presence of three specific T3 effector genes and with a T6SS gene sequence. Together, the phylogenetic and pathogenic differentiation among Xad strains justifies the installation of three pathovar epithets for the pathogens on aroids: X. phaseoli pv. dieffenbachiae comb. nov. for the strains isolated from Anthurium; X. phaseoli pv. syngonii comb. nov. for the strain isolated from Syngonium; and X. citri pv. aracearum comb. nov. for the strains isolated from Aglaonema, Xanthosoma and Dieffenbachia. It is proposed that phytosanitary regulations for xanthomonads on aroids are restricted to these three pathovars.     

Pathogenicity and molecular phylogenetic analysis reveal a distinct position of the banana fingertip rot pathogen among the Burkholderia cenocepacia genomovars

Banana (Musa spp.) is one of the most widely cultivated subtropical fruits around the globe. Banana cultivation has been extensively increased in southeastern Iran over the last two decades. Recently, banana fruits possessing rotten and blackened fingertip symptoms were observed in Sistan-Baluchestan, Iran. Isolation and characterization of the causal agent showed that the pathogen belongs to the multifaceted bacterial species Burkholderia cenocepacia. Pathogenicity tests and host range assays showed that the strains were pathogenic on banana, as well as carrot, onion and potato. All the strains were resistant to 50 mg L⁻¹ rifampicin and 200 mg L⁻¹ copper sulphate. Phylogenetic analysis of 16S rRNA and recA gene sequences showed that the strains belong to two different genomovars of B. cenocepacia (III-A and III-B), which also include environmental and cystic fibrosis associated strains of the species. The results obtained from recA phylogeny were confirmed using multilocus sequence analysis (MLSA), although MLSA showed that the banana strains were clustered as a novel phylogroup among the members of both genomovars. Banana-pathogenic B. cenocepacia strains isolated in Iran were different from the strains isolated in Taiwan, as the ‘B. cepacia epidemic strain marker’ reported in the Taiwanese strains was absent from Iranian strains. To the authors’ knowledge, this is the first MLSA-based study on the banana-pathogenic strains of B. cenocepacia. However, further in-depth molecular studies are needed to decipher the relationships between the banana fingertip rot pathogen and the clinical strains of B. cenocepacia.     

Consequences of the taxonomic revision of Xanthomonas axonopodis pv. dieffenbachiae and of the analysis of its associated pathogenicity for the recommendation of regulation (EPPO A2 List)

Xanthomonas axonopodis pv. dieffenbachiae, the causal agent of bacterial blight of Araceae (aroids), is a regulated pest in several countries and is included in the EPPO A2 List. Reference strains of Xanthomonas axonopodis pv. dieffenbachiae have recently been reclassified into the species Xanthomonas phaseoli, Xanthomonas citri and Xanthomonas euvesicatoria on the basis of different features, including multilocus sequence analysis, average nucleotide identity and homology in DNA–DNA hybridization analyses. Based on pathogenicity tests, Constantin et al. (2017) proposed naming the pathogens on aroids as X. phaseoli pv. dieffenbachiae, X. phaseoli pv. syngonii and X. citri pv. aracearum. Recommendations are made on how to deal with these changes for the group of pathogenic bacteria for Araceae. The name Xanthomonas axonopodis pv. dieffenbachiae on the EPPO List should be adjusted to the names proposed in the taxonomic study by Constantin et al. (2016). The current EPPO Diagnostic Standard is directed at strains pathogenic on Anthurium. They mainly belong to X. phaseoli pv. dieffenbachiae, but some also to X. citri pv. aracearum that are not detected by the EPPO Diagnostic Standard. Xanthomonas phaseoli pv. syngonii strains are also aggressive, but with a host range restricted to Syngonium. The pathogenicity specific to aroids of the bacterial isolates reclassified as Xanthomonas euvesicatoria was not confirmed and no pathovar epithet has been retained for these strains.     

Impact of bacterial spot outbreaks on the phytosanitary quality of tomato and pepper seeds

The impact of disease outbreaks on the phytosanitary quality of seeds was investigated for two pathosystems: tomato–Xanthomonas vesicatoria and pepper–Xanthomonas euvesicatoria. This study, which was performed in Italy and Serbia, aimed to evaluate the season‐to‐season transmission of phytopathogenic regulated bacteria associated with phytosanitary risks posed by seeds produced in areas where bacterial infections are possible. For each pathosystem, field plots were experimentally inoculated to simulate an initial infection rate of 1%, 5% and 15%. The area under the disease progress curve (AUDPC) was calculated for each field plot, the seeds produced were analysed to determine the contamination level and rate, and the plant‐to‐seed transmission was evaluated by a seedling grow‐out (SGO) assay. To investigate transmission under field conditions, a second‐year experiment was performed, wherein seeds collected from the first year were used to establish new field plots. During the first growing season, AUDPC values were positively correlated with the percentages of initial infection for each pathosystem. Seed contamination levels in pepper ranged from 34 to 100 CFU g^?1, and the contamination rate ranged from 1.50% up to 3.17% for X. euvesicatoria, whereas processing and fresh market tomato seeds produced both in Italy and Serbia were not infected by X. vesicatoria. During SGO assays and the second cropping year, no symptoms were observed in either tomato or pepper plants. Therefore, the calculated pepper seed contamination rate for X. euvesicatoria appeared to be less than the threshold necessary to initiate a disease outbreak. Finally, all seeds obtained during the second cropping year were uninfected.     

PM 7/110 (1) Xanthomonas spp. (Xanthomonas euvesicatoria,Xanthomonas gardneri,Xanthomonas perforans,Xanthomonas vesicatoria) causing bacterial spot of tomato and sweet pepper

Specific scope

This standard describes a diagnostic protocol for Xanthomonas spp. causing bacterial spot of tomato and sweet pepper (Xanthomonas euvesicatoria, Xanthomonas gardneri, Xanthomonas perforans, Xanthomonas vesicatoria) ¹ .

Specific approval and amendment

Approved in 2012–09.     

The genetic characterization of Xanthomonas arboricola pv. juglandis,the causal agent of walnut blight in Poland

Leaves and fruits of walnut trees exhibiting symptoms of bacterial blight were collected from six locations in Poland. Isolations on agar media resulted in 18 bacterial isolates with colony morphology resembling that of the Xanthomonas genus. PCR using X1 and X2 primers specific for Xanthomonas confirmed that all isolates belonged to this genus. In pathogenicity tests on unripe walnut fruits, all isolates caused typical black necrotic lesions covering almost the entire pericarp. Results of selected phenotypic tests indicated that characteristics of all isolates were the same as described for the type strain of Xanthomonas arboricola pv. juglandis. Genetic analyses (PCR MP, ERIC‐, BOX‐PCR and MLSA) showed similarities between the studied isolates and the reference strain of X. arboricola pv. juglandis CFBP 7179 originating from France. However, reference strains I‐391 from Portugal and LMG 746 from the UK were different. MLSA analysis of partial sequences of the fyuA, gyrB and rpoD genes of studied isolates and respective sequences from GenBank of pathotype strains of other pathovars of X. arboricola showed that the X. arboricola pv. juglandis isolates consisted of different phylogenetic lineages. An incongruence among MLSA gene phylogenies and traces of intergenic recombination events were proved. These data suggest that the sequence analysis of several housekeeping genes is necessary for proper identification of X. arboricola pathovars.     

Visualisation of <Emphasis Type="Italic">hrp</Emphasis> gene expression in <Emphasis Type="Italic">Xanthomonas euvesicatoria</Emphasis> in the tomato phyllosphere

The plasmid pUFZ75 conferred constitutive GFP expression on the bacterial pathogen Xanthomonas euvesicatoria (syn. X. campestris pv. vesicatoria). Colonisation of the tomato phyllosphere and invasion of tomato leaves by X. euvesicatoria was examined using both fluorescence and confocal laser scanning microscopy. Xanthomonas euvesicatoria established a limited population on the tomato leaf surface, primarily occupying the depressions between epidermal cells and around the stomata, prior to invasion of the leaf via the stomata and subsequent growth within the substomatal chamber and the leaf apoplast. Additionally, hrp-gfp fusions were used to report on the temporal and spatial expression of hrp genes during epiphytic colonisation and invasion. Xanthomonas euvesicatoria cells carrying hrpG- and hrpX-gfp reporter constructs were not fluorescent in vitro on non-hrp-inducing LB agar but did exhibit a low level of fluorescence on the leaf surface within 24 h of inoculation, particularly in the vicinity of stomata. Cells carrying hrpG- and hrpX-gfp fusions exhibited high levels of fluorescence 72 h after inoculation in the substomatal chamber and the leaf apoplast. Cells carrying the hrpF-gfp fusion were slightly fluorescent on LB agar and showed no further increase in fluorescence on the leaf surface by 24 h after inoculation, but did show a significant increase in fluorescence 72 h after inoculation in the substomatal chamber and apoplast. The apparent low-level induction of the regulators hrpG and hrpX on the tomato leaf surface may suggest that some of the genes of the X. euvesicatoria HrpG/HrpX regulon are up- or down-regulated prior to invasion of the stomata while still on the leaf surface.     

Epiphytic Curtobacterium flaccumfaciens strains isolated from symptomless solanaceous vegetables are pathogenic on leguminous but not on solanaceous plants

In Iran, during 2013–16, 16 Gram‐positive corynebacteria‐like strains were recovered from the epiphytic parts of solanaceous vegetables including eggplant, pepper and tomato. The strains were recovered accidentally as a result of monitoring for other bacterial pathogens in solanaceous fields. The strains were phenotypically different from Clavibacter michiganensis strains. Although none of the strains were pathogenic on their host of isolation or on any other solanaceous plants, 12 out of 16 strains were pathogenic on common bean, cowpea, mung bean and soybean. Colonization by strains was observed on maize, zucchini, faba bean, honeydew melon, rapeseed, sugar beet and sunflower plants under greenhouse conditions. In PCR tests, the primer pair CffFOR2/CffREV4, specific for Curtobacterium flaccumfaciens pv. flaccumfaciens, enabled the amplification of the appropriately sized fragment in 12 out of 16 strains, and all 12 strains were pathogenic on dry beans. Phylogenetic analysis, using the gyrB and recA genes, showed all 16 bacterial strains clustered within several pathovars of C. flaccumfaciens. A nonpathogenic yellow‐pigmented strain (Xeu15) was clustered with the type strains of C. flaccumfaciens pv. betae and C. flaccumfaciens pv. oortii. Bacteriocin profiling assays revealed no significant differences among the pathogenic and nonpathogenic strains. Host range and population dynamics of four representative strains on 17 plant species showed population build‐up of the strains only on common bean, cowpea, wheat and red nightshade plants. The results provide important insights into the possible role of nonhost plants as reservoirs of plant pathogenic bacteria, which has important implications in plant disease epidemiology and management.     

A pith necrosis caused by Xanthomonas perforans on tomato plants

Pith necrosis is a common disease of tomato in Europe, mainly caused by Pseudomonas corrugata and other soil-borne species of Pseudomonas. During 2011–2012 a survey was conducted in soil-grown tomato crops in southeastern Sicily (Italy). Plants showed pith necrosis, brown discolouration of the vascular tissues, leaf chlorosis and sometimes wilting of leaves. Thirty bacterial isolates from symptomatic tissues, forming colonies on NA and KB, were identified by morphological, biochemical and physiological tests. Among them, seven isolates were analyzed for their 16S rDNA and 16S–23S spacer region sequence that resulted in 99 % identity to that of the Xanthomonas perforans type strain (GenBank accession number GQ46173over 2.085 bp.). Additional sequences of fusA, gapA, gltA, gyrB, lacF, and lepA from one selected isolate were 100% identical to sequences of the Xanthomonas perforans type strain. X. perforans local isolates showed similar genomic patterns with REP-PCR and fAFLP, and were clearly distinguished from other Xanthomonas spp. type strains. In stem-inoculation assays, bacteria isolated from symptomatic tomato plants identified as P. fluorescens, P. putida, P. marginalis, P. citronellolis, P. straminea, and Pantoea agglomerans induced discolouration of vascular tissues, while Pectobacterium carotovorum subsp. atrosepticum isolates induced soft rot. Conversely, the isolates here identified as Xanthomonas perforans were able to induce pith necrosis, vascular discolouration, longitudinal splits and external lesions on stems. This report of X. perforans causing pith necrosis on tomato represents a potentially serious problem that may limit the productivity of tomato crops.     

Phenotypic and Genotypic Characterization of Xanthomonas campestris pv. zinniae Strains

During 1997 and 1998, serious outbreaks of bacterial leaf spot disease were observed on zinnia plants grown in home and commercial gardens in Ohio, USA. Twenty-two strains of Xanthomonas campestris pv. zinniae, isolated from diseased zinnia plants and contaminated seeds, were identified based on morphological, physiological and biochemical tests, fatty acid methyl ester analyses and pathogenicity tests on zinnia cv. Scarlet. Host range studies indicated that all of the X. campestris pv. zinniae strains were pathogenic on zinnia and tomato, but not on cabbage, lettuce, pepper and radish. The phenotypic and genotypic relationships among the strains determined based on serological reaction pattern, fatty acid profiles, repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) fingerprints and sequence analysis of the 16S–23S rDNA spacer region suggested that X. campestris pv. zinniae strains were closely related to each other, but clearly distinct from other Xanthomonas species including X. campestris pv. campestris, X. axonopodis pv. vesicatoria, X. vesicatoria and X. hortorum pv. vitians tested in this study. The results also demonstrated that rep-PCR fingerprinting is rapid, reliable and the most practical method for routine detection and identification of X. campestris pv. zinniae strains.     

Pathogenicity and phylogenetic analysis of Clavibacter michiganensis strains associated with tomato plants in Iran

During 2013–2016, 277 tomato fields were surveyed across Iran to monitor the status of bacterial canker of tomato, caused by Clavibacter michiganensis subsp. michiganensis. Altogether, 450 plant samples were collected, both with and without symptoms, from which 35 bacterial strains were recovered. These were positive for the PCR test performed using the Clavibacter‐specific primer pair CMR16F1/CMR16R1. Based on the phylogeny of the gyrB gene sequences, 31, three and one of the 35 strains were identified as C. michiganensis, Microbacterium sp. and Agrococcus sp., respectively. The 31 strains of C. michiganensis were further identified as C. michiganensis subsp. michiganensis (23 strains), C. michiganensis subsp. tessellarius (six strains) and Clavibacter spp. (two strains). This was subsequently confirmed by multilocus sequence analysis (MLSA) of five housekeeping genes (atpD, gyrB, ppk, recA and rpoB). In pathogenicity tests, all 23 strains induced wilting symptoms on tomato plants in greenhouse conditions, while no symptoms were observed on eggplant, bell pepper and chili pepper plants. All evaluated pathogenicity determinant genes (celA, pat‐1, tomA, ppaA, chpC and chpG) were detected in 18 out of 31 C. michiganensis strains, using eight specific primer pairs. Estimation of the number of nucleotide differences, sequence similarity matrix and MLSA clustered two peach‐coloured strains (Tom495 and Tom532) separately from all nine previously described subspecies, thereby suggesting these two strains are a new subspecies of C. michiganensis. However, a detailed taxonomic study using multiphased molecular approaches is needed to delineate a formal taxonomic name for these atypical strains.     

Resistance to Xanthomonas perforans race T4 causing bacterial spot in tomato breeding lines

Tomato (Solanum lycopersicum) is the second most important vegetable crop in the world. Bacterial spot (BS) of tomato, caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri, results in severe loss in yield and quality due to defoliation and formation of lesions on fruits, respectively. Currently management practices do not offer effective control under conditions of high disease pressure. Thus, developing BS resistance is a critical priority for tomato growers in order to minimize crop losses. Sixty‐three advanced tomato breeding lines, heirlooms and wild tomato lines with diverse genetic backgrounds were screened under greenhouse and field conditions for BS resistance using X. perforans race T4, which was found to be a prevalent race in North Carolina. Race T4 isolate 9 was used to inoculate the plants by spraying, and disease severity was measured using the Horsfall–Barratt scale. Tomato lines 74L‐1W(2008), NC2CELBR, 081‐12‐1X‐gsms, NC22L‐1 (2008) and 52LB‐1 showed resistance to BS in the field and/or greenhouse trials. These lines were derived from S. pimpinellifolium L3707. Screening L3707 followed by development of a mapping population and mapping resistance genes might be useful for breeding resistance against BS in future breeding programmes.     

Polyphasic phenotypic and genetic analysis reveals clonal nature of Xanthomonas axonopodis pv. punicae causing pomegranate bacterial blight

Yellow-pigmented bacteria isolated from blight-affected pomegranate leaves and fruit across seven Indian states in epidemics during the years 2008–2016 were characterized and identified using phenotypic and genotypic tools. All bacterial isolates shared phenotypic traits such as colony morphology, NaCl and pH sensitivity and fuscan production, and caused typical lesions on pomegranate plants upon artificial inoculation. Analysis of 16S ribosomal DNA and 16S–23S rDNA intergenic spacer sequences confirmed their identity as Xanthomonas axonopodis pv. punicae. The new isolates collected after 2000 were compared with an old isolate from the 1950s using polyphasic taxonomic approaches including multilocus sequence analysis (MLSA). Nucleotide polymorphism in 24 isolates for nine genomic loci (dnaK, fyuA, gyrB (Young), gyrB (Almeida), rpoD, fusA, gapA, gltA and lepA) showed minor variations in loci fyuA and gyrB. Isolates were grouped into four nearly identical sequence types, ST1, ST2, ST3 and ST4, based on their allelic profiles, ST3 being widespread in Indian states. Molecular phylogenetic analysis of concatenated 5690 bp with other Xanthomonas pathovars revealed its close genetic similarity with the X. citri group. The blight outbreak in diverse geographical locations is attributed to a re-emerged clonal population of X. axonopodis pv. punicae on a genetically homogenous pomegranate cultivar. The latently infected vegetative planting material of elite pomegranate cultivars contributed to the dissemination of the bacterial inoculum. This study highlights and forewarns of the role played by the clonally propagated elite pomegranate cultivars in disseminating and sustaining clonal populations of this bacterial plant pathogen in many Indian states.     

The first report and control strategies of Tuta absoluta in Iran

In Iran, the tomato growing area is about 150 000 ha, mostly located in the south of the country. The Iranian Plant Protection Organization and inspection service in Iranian Research Institute of Plant Protection (IRIPP) prepared a monitoring program for this pest in 2009 and 2010. A technical guideline was issued and distributed among PPO inspectors. For the first time in November 2010, samples were collected by Uromiyeh PPO on tomato from Uromiyeh in Azarbaijan province in North West Iran. The specimens found in these samples were identified as Tuta absoluta. Three months later in January 2011, pheromone traps were placed in tomato growing areas in Borazjan, Busher province, to detect and monitor this pest. T. absoluta was identified, based on adult morphology and on male genitalia from moths collected in 5 of these traps during January 2011. More pheromone traps were put into place covering the entire tomato growing area throughout the country. As of June 2011, the pest was detected in 24 different locations. This is the first report of T. absoluta in Iran. T. absoluta is a very serious pest for tomato, and an outbreak of this pest is expected during the crop cycle in autumn and winter 2011–2012 in the south of Iran. Thus, based on experiences in other countries an IPM program according to available tools and materials was developed.     

Identification of a genetic lineage within Xanthomonas arboricola pv. juglandis as the causal agent of vertical oozing canker of Persian (English) walnut in France

A new bacterial disease of Persian (English) walnut (Juglans regia) has been observed in France. This disease, called vertical oozing canker (VOC), is characterized by vertical cankers on trunks and branches of affected walnut trees with oozing exudates. To determine the aetiology of the disease, a study was carried out in 79 walnut orchards and nurseries located in southeastern and southwestern France. Bacterial analysis from diseased samples yielded 36 strains identified as Xanthomonas arboricola and 32 strains identified as Brenneria nigrifluens on the basis of biochemical tests. The causal agent of VOC was identified as X. arboricola by pathogenicity tests on walnut. Fluorescent amplified fragment length polymorphism (F‐AFLP) was carried out on 36 strains of X. arboricola collected in this study, 24 strains of X. arboricola pv. juglandis isolated from walnut blight symptoms and one strain of X. arboricola pv. corylina included as an outgroup. Based on cluster analysis of F‐AFLP data, most X. arboricola strains responsible for main VOC outbreaks showed a high degree of similarity, forming a cluster clearly separate from strains of X. arboricola pv. juglandis isolated from walnut blight symptoms. It is suggested that VOC is caused by a distinct genetic lineage within the pathovar juglandis of X. arboricola that is also able to cause classical bacterial blight symptoms on walnut leaves and fruits.     

Characterization and pathogenicity assessment of Plectosphaerella species associated with stunting disease on tomato and pepper crops in Italy

This study follows a survey carried out in 2012 and 2013 on tomato and pepper crops in the Foggia province (southern Italy), for morphological, molecular and pathogenicity analyses of Plectosphaerella fungi. The Plectosphaerella genus includes several species that are pathogens of horticultural plants. The survey identified tomato and pepper crops that showed abundant wilt, leaf yellowing, and discolouration and necrosis of roots, plus collar and stem symptoms. Different fungi including Plectosphaerella spp. were isolated from tissues with and without symptoms. Subsequent molecular and morphological studies identified first records of P. citrulli infecting tomato and pepper, and P. pauciseptata and P. ramiseptata infecting pepper. Pathogenicity testing confirmed that most isolated species of Plectosphaerella caused symptoms on tomato and pepper, with P. ramiseptata the most aggressive. On the basis of these data, it is considered that Plectosphaerella species may cause stunting disease in tomato and pepper.