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Laala S.,Cncc Center National Of Controle Et Of Certification Des Semences Et Plants | Manceau C.,Laboratoire Of La Sante Des Vegetaux | Valentini F.,Mediterranean Agronomic Institute MAIB | Kerkoud M.,Diag Gene | Kheddam M.,Cncc Center National Of Controle Et Of Certification Des Semences Et Plants
Journal of Plant Pathology | Year: 2012

During field surveys conducted in Spring and Summer 2010-2011, typical fire blight symptoms were observed on twigs and branches of pear (Pyrus communis) and apple (Malus domestica) in Algerian commercial orchards located in the areas of Algiers, Blida, Tipaza and Boumerdes. The disease was observed in 284 orchards, mainly on pear cv. Santa Maria and on apple cvs Royal gala and Golden delicious. Bacterial colonies were isolated on King's medium B (KB) and the semi-selective medium CCT (cycloheximide, cristal violet and thallium nitrate). Bacterial isolates displayed biochemical patterns typical of Erwinia amylovora and reacted positively in a serological slide agglutination test. Pathogenicity of bacterial isolates was confirmed by inoculating immature pear fruits of cv. Conference. The identity of the isolates was further confirmed by nested-PCR, and rep-PCR. A sequenced DNA fragment (713 bp) of the recA gene (accession No. JN812979) matched with 100% identity all E. amylovora recA DNA sequences available in GeneBank.


Elbeaino T.,Mediterranean Agronomic Institute MAIB | Mortada C.,Mediterranean Agronomic Institute MAIB | Digiaro M.,Mediterranean Agronomic Institute MAIB | Choueiri E.,Lebanese Agricultural Research Institute
Acta Horticulturae | Year: 2012

A survey was carried out in the main fig-growing areas of Lebanon (Bekaa and Mount Lebanon) in 2006-2008. A total of 102 samples were collected and tested by RT-PCR for the presence of Fig mosaic virus (FMV), Fig leaf mottle-associated virus 1 (FLMaV-1), Fig leaf mottle-associated virus 2 (FLMaV-2), Fig mild mottle associated virus (FMMaV) and a still unclassified isometric virus of the Tymoviridae family (hereafter indicated as FFkaV) using virus-specific primers. About 90% of the trees were infected with at least one virus, with mixed infections in ca. 46% of the samples. FLMaV-1 closterovirus was the prevailing virus (47% infection), especially in Mount Lebanon (95%) and on 'Aswad' (80%), followed by FMV Emaravirus (42.2% infection), which was particularly widespread in North Bekaa (68.1%) on 'Biadi' (50.8%). Two more viruses of the family Closteroviridae, FLMaV-2 and FMMaV, were detected respectively in 29.4 and 26.5% of the samples, with FLMaV-2 particularly widespread in north Bekaa (57.4%) on 'Biadi' (39.4%). FFkaV was detected in 13.7% of the samples, with an infection peak in 'Houmairi' (40%).


Al-Abdallah O.,Mediterranean Agronomic Institute MAIB | Elbeaino T.,Mediterranean Agronomic Institute MAIB | Valentini F.,Mediterranean Agronomic Institute MAIB | Digiaro M.,Mediterranean Agronomic Institute MAIB | Farinelli D.,University of Perugia
Acta Horticulturae | Year: 2012

A survey was carried out to assess the sanitary status of olive trees in a collection plot in Perugia (Umbria, Italy). A total of 95 samples were tested by RT-PCR to check for the presence of the following olive-infecting viruses: Arabis mosaic (ArMV), Cherry leaf roll (CLRV), Cucumber mosaic (CMV), Olive leaf yellowing-associated (OLYaV), Olive latent ringspot (OLRSV), Olive latent -1 (OLV-1), Olive latent -2 (OLV-2), and Strawberry latent ringspot (SLRSV). About 82% of the plants were infected with at least one virus. All the tested viruses were present, with the prevalence of CMV and OLRSV (more than 30%), followed by OLYaV (21.1%) and SLRSV (19%). DsRNA and mechanical transmission assays were also applied to all PCR-negative samples. Eight out of the 17 samples tested showed different dsRNA patterns, thus suggesting that they were infected with viruses different from those previously checked by PCR. This study allowed the identification of 9 "virus-free" and 39 "virus-tested" (i.e. olive plants free from SLRSV, ArMV, CLRV, OLYaV and OLV-1, according to the Italian certification protocols) candidate clones which could potentially be used as mother plants in future Certification programmes.


Yaseen T.,Mediterranean Agronomic Institute MAIB | D'Onghia A.M.,Mediterranean Agronomic Institute MAIB
Acta Horticulturae | Year: 2012

Fusarium root rot and dry rot are destructive diseases of citrus trees that gradually affect plants under biotic or abiotic stress. Many Fusarium spp. are supposed to be the casual agents of these diseases and their identification could be of an extreme difficulty. In this work, Fusarium spp. were collected from commercial citrus orchards and nurseries in Italy, Tunisia, Greece and Egypt. Three Fusarium species (F. solani, F. oxysporum and F. proliferatum) were identified according to morphological and molecular characterization, thus F. solani and F. oxysporum were the most frequent isolated species and, accordingly, were grouped upon the sequence of β-tubulin and α-Elongation Factor loci into nine clusters. Three pathogenicity characters were assessed: phytotoxicity of fungi excretions, capacity to colonize the surface of citrus host plant and ability to colonize the internal tissues. All trials were carried out on citrus, 'Carrizo' citrange. Symptoms of wilting were assessed over two months in phytotoxicity of culture filtrate trial. The results highlighted a significant correlation between phytotoxicity excretions and invasion ability. Nevertheless, no correlation was found between these two measures and the ability to colonize the surface of citrus seedlings. Despite the large variation existing among strains within the species, strains belonging to F. oxysporum showed a higher aggressiveness among all the characters tested, thus confirming the previous results obtained on the pathogenicity of F. oxysporum strains and F. sp. citri. Due to the fact that all the tested isolates were collected from orchards known to have dry root rot symptoms, and according to our finding regarding the higher aggressiveness of F. oxysporum isolates on citrus seedlings, a correlation might be suggested between Fusarium wilt disease affecting citrus seedlings and dry root rot disease observed on scaffold roots of trees in the orchards.


D'Onghia A.M.,Mediterranean Agronomic Institute MAIB | Di Terlizzi B.,Mediterranean Agronomic Institute MAIB
Acta Horticulturae | Year: 2012

Fruit trees in the Mediterranean area can be seriously compromised by pests and pathogens, which can be widely distributed or only localized in some countries or areas. Due to the climate change, new emerging pathogens may become dangerous for fruit tree crops. Furthermore, a number of destructive pests and pathogens are not yet present in the Mediterranean area and their potential entrance and spread can represent a serious threat for the sustainability of these crops. Within this context, the improvement of the quality of propagating materials of fruit tree species represents a fundamental option in the framework of the outcomes of the Barcelona declaration (1995), since it reduces dissemination of pests and pathogens among the countries through the free exchange of plant materials. The strategy conducted by CIHEAM/ MAIB, through the IPM Division, is aimed at facilitating the Barcelona process in the Region for propagating materials involving political organizations, scientific institutions, professional associations and farmers. Several important results were achieved through the training of executives, research and network actions in the region thereby implementing international cooperation programmes. Dedicated research networks were activated for the harmonization of technical protocols, procedures and regulations and for acquiring updated information on the sanitary status of fruit crops in most of the countries. Co-operation projects were promoted for the improvement of the fruit tree industry through the enhancement of the quality of nursery productions in different Mediterranean countries. Apart from international cultivars, several local genotypes of fruit tree crops have been clonally and sanitarily selected, thus contributing to the free exchange of this germplasm in the region. Through this long process, the free trade area of plant materials can be now envisaged among some countries in the Region.


Yahiaoui D.,Mediterranean Agronomic Institute MAIB | Djelouah K.,Mediterranean Agronomic Institute MAIB | D'Onghia A.M.,Mediterranean Agronomic Institute MAIB | Catara A.,University of Catania
Acta Horticulturae | Year: 2012

Citrus tristeza closterovirus (CTV), an insect-borne virus transmitted in nature by several aphid species in a semi-persistent manner, has historically posed a serious threat to the citrus industry worldwide. Up to date, the virus characterization and virus-vector relationship have been a key factor in understanding the disease epidemiology. The present research investigated the genetic variability generated within specific genomic regions of selected CTV isolates throughout the transmission by aphids. Isolates showing different genotype profiles and originating from Italy and Egypt were subjected to experimental transmission trials by a local biotype of Aphis gossypii (Glover) species, onto Mexican lime [Citrus aurantifolia (Christm.) Swingle] seedlings. The genotypes belonging to these CTV isolates were studied by using simultaneously multiple molecular markers (MMM) analysis, partial genome sequencing on CPg and single strand conformation polymorphism (SSCP) assays flanking the p18 and p20 genomic regions. The SSCP patterns obtained from the different sub-isolates were compared to those associated with their parental inoculum sources. In the present work, screening of slight CTV genomic variations in the aphid derived sub-isolates indicated variable changes in the studied proteins, regardless of the transmission abilities of the CTV isolates.


Gualano S.,Mediterranean Agronomic Institute MAIB | Santoro F.,Mediterranean Agronomic Institute MAIB | Djelouah K.,Mediterranean Agronomic Institute MAIB | D'Onghia A.M.,Mediterranean Agronomic Institute MAIB
Acta Horticulturae | Year: 2012

Citrus tristeza, caused by CTV, is the most destructive virus disease of Citrus spp. and its monitoring on a large scale is of great importance for the rapid application of control measures. To this aim a study on proximal and remote sensing was conducted for the identification of CTV-infected trees. The research was carried out in 2 infected commercial groves of 'Navelina' orange located in the CTV outbreak area of Apulia Region, Italy. The selected groves showed different virus infection rates after serological and molecular testings. Spectral signatures of selected trees were provided by the use of the HandHeld Post Dispersive Spectrometer in order to identify the vegetation indices correlated to CTV-infected and uninfected trees; these indices were produced by the algebraic combinations of reflected or emitted energy values measured in the different bands of the electromagnetic spectrum. Measurements highlighted a difference in the spectral signatures of CTV-positive trees with respect to the CTV-negative trees; thus, specific indices were selected for the implementation of a detection algorithm, which was applied to a processed multispectral satellite image. The elaborated images allowed the assessment of CTV infections in relation to different grades of canopy stress.


Abou Kubaa R.,Mediterranean Agronomic Institute MAIB | Yahiaoui D.,Mediterranean Agronomic Institute MAIB | Djelouah And K.,Mediterranean Agronomic Institute MAIB | D'Onghia A.M.,Mediterranean Agronomic Institute MAIB | Saponari M.,CNR Institute of Plant virology
Acta Horticulturae | Year: 2012

Citrus tristeza virus (CTV) has been considered a heavily destructive pathogen to the world's citrus industries. In the Mediterranean basin, despite the eradication programmes that have been undertaken in many countries, CTV is still a serious threat due to its wide dissemination and the predominant use of the susceptible sour orange as rootstock. Sixteen CTV isolates collected from Algeria, Italy, Montenegro and Palestine, maintained at the Mediterranean Agronomic Institute of Bari (MAIB), were characterized by using a set of primers encompassing similar sized DNA fragments from four reference strains (T30, T36, VT and T3). Among the studied CTV isolates, 10 were apparently pure and showed T30, T36 and VT genotypes, while the remaining isolates proved to be genotype mixture including VT-T3; T36-T30 and VTT36 groups. This finding highlighted the wide distribution of T30 genotype throughout the Mediterranean area and the occurrence of severe strains.


Digiaro M.,Mediterranean Agronomic Institute MAIB
Acta Horticulturae | Year: 2012

A brief account is given on the situation of Sharka disease in the Mediterranean countries. The recent developments in the domain of virus characterization, diagnosis, epidemiology, genetic resistance and control measures are briefly reviewed. The necessity to intensify and extend the territorial monitoring activity and the use of certified plant propagating material of stone fruits is strongly recommended.


Djelouah K.,Mediterranean Agronomic Institute MAIB
Acta Horticulturae | Year: 2012

A brief account is given on the present situation of tristeza disease in the Mediterranean countries. The recent developments in terms of presence, distribution, epidemiology and control measures are critically reviewed and analyzed. Emphasis is laid on the necessity to intensify and extend the local monitoring activity and the use of citrus certified plant propagating material.

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