First report and molecular characterization of citrus dwarfing viroid (CDVd) and citrus bark cracking viroid (CBCVd) on Citrus volkameriana in Egypt

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Occurrence and distribution of pome fruit viruses in Tunisia

The phytosanitary status of pome fruit trees was examined in Tunisia, in surveys conducted in spring 2009 and 2010, in the main Tunisian mother blocks. A total of 248 samples were collected (111 from apple, 106 from pear and 31 from quince), and tested for the presence of Apple chlorotic leaf spot virus (ACLSV) and Apple mosaic virus (ApMV) using ELISA and RT-PCR, and for Apple stem pitting virus (ASPV) using RT-PCR. 37% of the samples were infected by at least one virus. ACLSV was the most widespread virus (34% of samples), followed by ApMV (4%). Furthermore, molecular analysis showed that 69% of the sampled trees were infected and apple was the most infected species (80%), followed by pear (75%) and quince (10%). ASPV was the most prevalent virus (46%), followed by ACLSV (39%) and ApMV (10). Mixed infections occurred in several trees, and the most common combination was ASPV+ACLSV (23%). This is the first report on the presence of viruses infecting pome fruits in Tunisia

Direct tissue blot immunoassay for detection of Xylella fastidiosa in olive trees

A direct tissue blot immunoassay (DTBIA) technique has been compared with ELISA and PCR for detection of Xylella fastidiosa in olive trees from Apulia (southern Italy). Fresh cross-sections of young twigs and leaf petioles were printed onto nitrocellulose membranes and analyzed in the laboratory. Analyses of a first group of 61 samples gave similar efficiency for the three diagnostic techniques for detection the bacterium (24 positive and 36 negative samples), except for a single sample which was positive only with DTBIA and PCR. Similar results were obtained by separately analyzing suckers and twigs collected from different sectors of tree canopies of a second group of 20 olive trees (ten symptomatic and ten symptomless). In this second test the three diagnostic techniques confirmed the irregular distribution of the bacterium in the tree canopies and erratic detectability of the pathogen in the young suckers. It is therefore necessary to analyse composite samples per tree which should be prepared with twigs collected from different sides of the canopy. The efficiency comparable to ELISA and PCR, combined with the advantages of easier handling, speed and cost, make DTBIA a valid alternative to ELISA in large-scale surveys for occurrence of X. fastidiosa. Moreover, the printing of membranes directly in the field prevents infections spreading to Xylella-free areas, through movement of plant material with pathogen vectors for laboratory testing

Direct tissue blot immunoassay for detection of Xylella fastidiosa in olive trees

A direct tissue blot immunoassay (DTBIA) technique has been compared with ELISA and PCR for detection of Xylella fastidiosa in olive trees from Apulia (southern Italy). Fresh cross-sections of young twigs and leaf petioles were printed onto nitrocellulose membranes and analyzed in the laboratory. Analyses of a first group of 61 samples gave similar efficiency for the three diagnostic techniques for detection the bacterium (24 positive and 36 negative samples), except for a single sample which was positive only with DTBIA and PCR. Similar results were obtained by separately analyzing suckers and twigs collected from different sectors of tree canopies of a second group of 20 olive trees (ten symptomatic and ten symptomless). In this second test the three diagnostic techniques confirmed the irregular distribution of the bacterium in the tree canopies and erratic detectability of the pathogen in the young suckers. It is therefore necessary to analyse composite samples per tree which should be prepared with twigs collected from different sides of the canopy. The efficiency comparable to ELISA and PCR, combined with the advantages of easier handling, speed and cost, make DTBIA a valid alternative to ELISA in large-scale surveys for occurrence of X. fastidiosa. Moreover, the printing of membranes directly in the field prevents infections spreading to Xylella-free areas, through movement of plant material with pathogen vectors for laboratory testing

Characterization of Citrus tristeza virus isolates recovered in Syria and Apulia (southern Italy) using different molecular tools

Citrus tristeza virus (CTV) is the causal agent of the most important virus disease of citrus. CTV isolates differing in biological and molecular characteristics have been reported worldwide. Recently, CTV was detected in Syria in citrus groves from two Governorates (Lattakia and Tartous) and several CTV outbreaks have been reported in Apulia (southern Italy) since 2003. To molecularly characterize the CTV populations spreading in Syria and Italy, a number of isolates from each region was selected and examined by different molecular approaches including: Multiple Molecular Markers analysis (MMM), real time RT-(q)PCR, single strand conformation polymorphism (SSCP) of the major coat protein (CP) gene (P25), and sequence analysis of the CP (P25), P18, P20 and RdRp genes. SSCP analysis of CP25 yielded two distinct simple patterns among the Syrian isolates and three different patterns in the Italian isolates. Based on MMM analysis, all Syrian CTV isolates were categorized as VT-like genotype, whereas the Italian isolates reacted only with the markers specific for the T30 genotype. These findings were also confirmed by RT-qPCR and by sequencing analysis of four genomic regions. The Italian isolates had nucleotide identities which varied: from 99.5 to 99.8 for the CP gene; from 97.4% to 98.3% for the P18 gene; from 98.6% to 99.8% for the P20 and from 97.8% to 99.1% for the partial RdRp sequenced. High sequence identity was found for all genomic regions analyzed between the Syrian isolates (from 98.9% to 99.6%). These results show that the CTV populations spreading in Apulia and Syria are associated with different genotypes, indicating different potential impacts on the citrus trees in the field. Since in both areas the introduction of the virus is relatively recent, infected plants resulted to contain a single and common genotype, suggesting that CTV is spreading from the first outbreaks by aphids or local movement of autochthonous infected plant material

Healthy citrus propagative material to avoid the introduction of transboundary pests/pathogens (BIOFRUITNET Practice Abstract)

The use of 'healthy' plant material and efficient quarantine measures is economically and environmentally more efficient than eliminating the newly introduced pests/diseases. Practical recommendation The use of 'healthy' plant material and efficient quarantine measures is economically and environmentally more efficient than eliminating the newly introduced pests/diseases. • The choice of nursery plants is the first action toward sustainable and quality production. • The use of healthy citrus propagative material is the only valid strategy to prevent the introduction of devastating pests/pathogens such as the recently introduced Orange spiny whitefly in Italy, Croatia and Greece. mealybug Delottococcus aberiae in Spain, which are seriously threatening the Mediterranean citriculture. • If the certified citrus propagative material is unavailable in the specific EU regulatory context of organic plant material production, the farmers can rely on the conventional certified propagative material in the framework of the conversion period. • The citrus propagative material needs to be imported into the EU countries only if accompanied by a phytosanitary certificate confirming their compliance with the EU legislation

Virus de la mosaïque du pepino: une grave menace pour les plants de tomate dans le monde entier

Tomato (Solanum lycopersicum) is one of the widely grown crops worldwide. It is consumed in various forms and has excellent nutritional values. Presently, this crop is facing a serious threat to its yield and survival because of a potexvirus infection. One of the potexvirus species hampering tomato productions worldwide is Pepino mosaic virus (PepMV). This emerging virus is one of the most destructive plant diseases destroying tomato crops globally. It has spread to many countries worldwide including France, Italy, the UK, Poland, Belgium, the USA, Canada and China. PepMV genome consists of a positive-sense, single-stranded RNA molecule, approximately 6.4 kb in length. The genomic RNA contains five open reading frames (ORFs) encoding for the coat protein (CP), the putative viral polymerase (RdRp) and the triple gene block (TGB) proteins. PepMV is efficiently transmitted mechanically. In other studies, seed transmission has been demonstrated. This article provides an overview of PepMV symptoms, transmission, different strains of PepMV, its genome organization and strategies employed for controlling it. The knowledge about the recent progress in the study of PepMV would help develop novel strategies for its control in agriculture. Keywords: PepMV, Tomato, potexvirus, genome organization, transmission, control.La tomate (Solanum lycopersicum) est l’une des cultures largement cultivées dans le monde entier. Elle est consommée sous diverses formes et possède d’excellentes valeurs nutritionnelles. À l’heure actuelle, cette culture est confrontée à une grave menace pour son rendement et sa survie en raison de l’infection par les potexvirus. Un des potexvirus qui entravent la production des tomates dans le monde entier est le virus de la mosaïque du pepino (PepMV). Ce virus émergent est l’une des maladies des plantes les plus destructrices qui détruisent la culture de tomate à l’échelle mondiale. Le virus s’est propagé dans de nombreux pays, y compris la France, l’Italie, le Royaume-Uni, la Pologne, la Belgique, les États-Unis, le Canada et la Chine. Le génome du PepMV se compose d’une molécule d’ARN simple brin à polarité positive, d’environ 6,4 kb de longueur. L’ARN génomique contient cinq cadres ouverts de lecture (ORF) codant pour la protéine de la capside (CP), La protéine de la réplicase (RdRp) et la protéine de bloc génique triple (TGB). PepMV est transmis de manière efficace mécaniquement. Dans d’autres études, la transmission par les semences a été démontrée. Cet article donne un aperçu sur les symptômes, la transmission, les différentes souches du PepMV, son organisation et les stratégies utilisées pour contrôler le génome. Les connaissances des progrès récents dans l’étude du PepMV pourraient aider à développer de nouvelles stratégies pour son contrôle dans le secteur agricole. Mots clés: PepMV, Tomate, potexvirus, génome, transmission, contrôle

An evaluation of some eco-friendly biopesticides against Bemisia tabaci on two greenhouse tomato varieties in Egypt

Th is study has two main approaches. First, it exploits the susceptibility of tomato cultivars as a prophylactic measure to detect auto resistance characters of the tested tomato varieties against Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Secondly, it evaluates the efficacy of different bio-rational insecticides against B. tabaci under greenhouse conditions. The results exhibited a special significance in B. tabaci infestation suitability between the two tomato varieties with a high infestation significance found in the Shifa F1 hybrid tomato variety compared to the Savera F1 hybrid tomato variety in the fi rst plantation period. Subsequently, in the second plantation period, there was a significant difference between the two tomato varieties. Bemisia tabaci showed a preference for the Shifa F1 hybrid over the Savera F1 hybrid tomato variety. Th ese diff erences occurred during the 1st, 2nd, 4th, 6th, 7th, 8th, and 10th weeks. In the experimental trial for the efficacy of eco-friendly biorational insecticides, spinosad, azadirachtin, Beauveria bassiana and Metarhizium anisopliae, there were significant differences between the treated and untreated plants during the two plantation periods. A high efficacy of spinosad on the B. tabaci population was found. Bemisia tabaci infestation under all the applications was reduced from 50 to 94.61% for the two plantation periods. This obvious decrease in B. tabaci population increase attention to benefits of the different bio-rational insecticides

Socio-Economic Risks Posed by a New Plant Disease in the Mediterranean Basin

Xylella fastidiosa (Wells 1987, hereafter Xf), the causal agent of several devastating plant diseases, is threatening new countries of the Euro-Mediterranean, Balkans, Middle East, and North Africa (MENA) regions. In this perspective, a study was carried out to: (a) explore the potential establishment and spread and losses caused by Xf in Euro-Mediterranean countries (i.e., France, Greece, Italy, Portugal, and Spain) and the Balkans (i.e., Albania, Bosnia and Herzegovina, Croatia, Montenegro, North Macedonia, Serbia, and Slovenia); (b) assess the potential introduction of Xf in the MENA countries (i.e., Algeria, Egypt, Israel, Jordan, Lebanon, Libya, Morocco, Palestine, Syria, Tunisia, and Turkey); and (c) project the socio-economic impacts of Xf on olives, grapes, citrus, and almonds in these countries. A novel socio-economic risk assessment technique was developed and applied for these purposes. It revealed that Albania had the highest risk for Xf dispersal. In addition, the risk assessment also confirmed the vulnerability of Euro-Mediterranean countries in terms of Xf dispersal. In the MENA and Balkans regions, countries with fragmented and small farms are likely to face the worst social impacts, whereas the Euro-Mediterranean region runs the highest economic losses on the target crops

Original Article. An evaluation of some eco-friendly biopesticides against Bemisia tabaci on two greenhouse tomato varieties in Egypt

Th is study has two main approaches. First, it exploits the susceptibility of tomato cultivars as a prophylactic measure to detect auto resistance characters of the tested tomato varieties against Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Secondly, it evaluates the efficacy of different bio-rational insecticides against B. tabaci under greenhouse conditions. The results exhibited a special significance in B. tabaci infestation suitability between the two tomato varieties with a high infestation significance found in the Shifa F1 hybrid tomato variety compared to the Savera F1 hybrid tomato variety in the fi rst plantation period. Subsequently, in the second plantation period, there was a significant difference between the two tomato varieties. Bemisia tabaci showed a preference for the Shifa F1 hybrid over the Savera F1 hybrid tomato variety. Th ese diff erences occurred during the 1st, 2nd, 4th, 6th, 7th, 8th, and 10th weeks. In the experimental trial for the efficacy of eco-friendly biorational insecticides, spinosad, azadirachtin, Beauveria bassiana and Metarhizium anisopliae, there were significant differences between the treated and untreated plants during the two plantation periods. A high efficacy of spinosad on the B. tabaci population was found. Bemisia tabaci infestation under all the applications was reduced from 50 to 94.61% for the two plantation periods. This obvious decrease in B. tabaci population increase attention to benefits of the different bio-rational insecticides