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This article reports on the profiles of the National Agricultural Research Systems (NARS) in the three Maghreb countries: Algeria, Morocco and Tunisia, through their research policies, human resources, governance, funding and scientific production. A bibliometric study was carried out for the three selected countries based on the Scopus database covering the period between 2005 and 2019. The research shows the distinctive case of Tunisian growth of scientific production compared to the other two countries; it also stresses the universities' emergence as a major research actor, thus challenging the predominance of the public mission-oriented institutions dedicated to agriculture and veterinary sciences. Finally, it indicates significant differences between the three countries concerning governance and funding, and human resources. Overall, the NARS in the three countries are still very fragile, and a need for significant changes in the research policy making is certainly required to overcome these shortcomings. [ABSTRACT FROM AUTHOR]

Recent occurrence in Tunisia of Citrus blast and black pit disease, caused by Pseudomonas syringae pv. syringae (Pss), the few available antibacterial chemicals, and the increasing resistance of Pss to copper sulfate highlighted the need for new antibacterial agents. In vitro analysis of the antagonistic activity of fifty-four native epiphytic bacterial isolates from the Citrus phyllosphere towards pathogenic Pss resulted in the selection of eight potential biocontrol strains according to their various antagonistic activities. Based on analysis of the (partial) 16S rRNA gene sequence and the rpoD housekeeping gene, five isolates were presumptively identified as Pseudomonas atacamensis (strains Y28, Y58 and Y128), P. cremoris (strain Y40), and P. lactis (strain Y21). In vivo test of these antagonistic strains showed no pathogenicity towards plant tissues. Three strains (Y28, Y128 and Y21) exhibited considerable inhibitory activities and significantly reduced disease severity in five Citrus cultivars (Cassar, Eurêka, Maltaise, Washington Navel and Pomelo) on shoots, leaves and fruits. Determination of genes coding for antibiotic production showed the presence of gacA gene in the five strains mentioned above. However, the genes prnD, pltC, pltB, phlD and phzC as well as phzD (and their homologs phzF and phzA), described earlier for Pf-5, were not detected among the tested Tunisian antagonistic Pseudomonas strains. This study presents the first description of P. atacamensis, P. cremoris, and P. lactis as potential biocontrol agents. The characterized bacterial strains may be considered as potential sources of novel bioactive metabolites as well as promising candidates to develop new biocontrol agents for sustainable control of Citrus. blast and black pit disease. [ABSTRACT FROM AUTHOR]

Pistachio (Pistacia vera L.) cultivation under rainfed conditions of the South Mediterranean has not been studied in depth. Under changing climate conditions, knowledge of cultivar and rootstock performances allows for the optimal use of genetic resources to improve yield and nut quality. This study aimed to evaluate growth, yield, and fruit characteristics of 'Mateur' and 'Achouri' pistachio cultivars grafted on P. vera and P. atlantica rootstocks grown in northeastern Tunisia. The research was based on three years worth of monitoring of growth, yield and fruit quality. Results showed that annual bio-climatic features had significant effects on all studied parameters. The 'Mateur' cultivar showed higher vigor and fruit yield than 'Achouri'. Fruit production was higher in P. atlantica rootstock for 'Mateur' but similar in both studied rootstocks for 'Achouri'. Kernel fat contents (40.7–46.8%) and fatty acid profiles were low or not affected by cultivar, rootstock and their combination. Oleic acid (C18:1) was the major fatty acid (68.94–69.22%) in kernel oil. The unsaturated/saturated fatty acid and oleic/linoleic acid ratios indicated that nuts obtained had high quality. The lower performances of 'Achouri' cultivar in the studied conditions may be related to low acclimation ability of this cultivar. These conditions, however, seem to be suitable for both studied rootstocks. [ABSTRACT FROM AUTHOR]

Citrus blast and black pit caused by Pseudomonas syringae pv. syringae (Pss) is the only bacterial disease reported in Tunisian Citrus orchards. The phylogenetic relationship between Pss strains was studied based on multilocus sequence analysis (MLSA), using partial sequences of housekeeping genes rpoD, rpoB, gyrB, cts, and pfk for 14 representative Pss Citrus strains, including the reference strain LMG5496. The MLSA revealed that the studied Tunisian Citrus strains are closely related to LMG5496 and cluster in phylogroup 02. Based on the cts gene, the majority of Citrus strains clustered in clades "a" and "b". However, five strains were placed in a newly defined clade "g". We describe the presence of six different type III secreted effectors (T3SEs). These were found with frequencies of 100% for the effector hopAN1 and the helper hrpK1, 65% for hopT1‐2, and 14% for hopN1, hopR1, and hopQ1‐2. Investigation of copper resistance showed that 67% of our Pss Citrus strains from Tunisia are resistant to copper sulphate in vitro, and the copper resistance genes copABCDR were detected in 23% of the strains. Our results present new data concerning the genetic diversity and phylogeny, presence of T3SEs, and copper resistance within the Pss populations that affect Citrus in Tunisia. [ABSTRACT FROM AUTHOR]

The article offers information on the plant disease caused by the phytopathogenic isolates of Rhodococcus fascians, a Gram-positive bacterium. It discusses that the bacteria cause disease on numerous plants by inducing fasciation and leafy galls. It mentions that the bacteria altered plant morphology resulting from these infections cause serious economic losses to ornamental industries.

Threats of desertification have been projected for the Mediterranean basin under relatively minor warming and drying scenarios. This situation raises the need for mitigation strategies and adaptation of crop production. Crop vulnerability assessment is therefore needed. In Tunisia, olive culture is a major activity. In some cases, olive is the only crop able to grow in local conditions. However, olive production may be among the more vulnerable systems to climate change since perennial crops adapt slowly. No studies have been dedicated to vulnerability evaluation of olive production. Here, the vulnerability of Tunisian olive trees to drought was assessed under extremely low precipitation levels, of 50% of normal precipitation, from 1999 to 2002. The impact of drought was quantified using a severity scale with three levels. A map of the impact of drought on olive trees was constructed for all Tunisian olive groves. We found that the number of wilting olive trees in 2002 was 7.8 millions of about 60 millions trees. A correlation was observed between olive tree affection by drought and olive orchard age. Thus, under the same drought conditions, senescent orchards were less resistant to drought than young ones. Locally, data showed that compact soils and soils containing more than 1% gypsum were not suitable for olive growth under drought. [ABSTRACT FROM AUTHOR]

We observed for the first time crown gall symptoms in an orchard of olive trees (Olea europaea) of the variety ‘Chemlali’ – the most widely grown cultivar in Tunisia – in the governorate of Kairouan in central Tunisia. Isolations from symptomatic tissues yielded bacteria that were identified as members of the species complex Agrobacterium tumefaciens using molecular techniques. The isolates were then evaluated for their pathogenicity by inoculating the indicator plant Kalankoë daigremontiana. The virulence of three isolates (O7, O9 and O11) was assessed by PCR amplification of part of the vir region of the Ti-plasmid of Agrobacterium and further confirmed for the O7 isolate by inducing the formation of tumours on ‘Chemlali’ olive seedlings. These results confirm the susceptibility of the olive tree to Agrobacterium tumefaciens, as previously reported by other researchers in Algeria, Jordan, Australia and Argentina. [ABSTRACT FROM AUTHOR]

Olive trees (cv. Chemlali) showing typical symptoms of wilt and dieback were collected from several areas in Tunisia. Visual diagnostic, isolation and microscopic observations identified the causal pathogen as Verticillium dahliae. The pathotype was determined using specific primers pairs for D (defoliating) and ND (non-defolitating) . Artificial inoculation of olive plants resulted in typical wilting with defoliation, proving that the isolate tested was pathogenic on olive, and this isolate belongs to the D pathotype. This is the first report of the defoliating pathotype causing wilting disease on olive in Tunisia. [ABSTRACT FROM AUTHOR]

The analysis of housekeeping recA gene sequences from 138 strains from 13 species or genomic species of Agrobacterium, nine being biovar 1 genomospecies, and the others Agrobacterium larrymoorei, Agrobacterium rubi, Agrobacterium sp. NCPPB 1650, and Agrobacterium vitis and one 'former' Agrobacterium species, Rhizobium rhizogenes, led to the identification of 50 different recA alleles and to a clear delineation of the 14 species or genomospecies entirely consistent with that obtained by amplified fragment length polymorphism (AFLP) analysis. The relevance of a recA sequencing approach for epidemiological analyses was next assessed on agrobacterial Tunisian isolates. All Tunisian isolates were found to belong to the Agrobacterium tumefaciens/biovar 1 species complex by both biochemical tests and rrs sequencing. recA sequence analysis further permitted their unambiguous assignment to A. tumefaciens genomospecies G4, G6, G7, and G8 in total agreement with the results of an AFLP-based analysis. At subspecific level, several Tunisian recA alleles were novel, indicating the power and accuracy of recA-based typing for studies of Agrobacterium spp. [ABSTRACT FROM AUTHOR]

Ripe and overripe olive fruits (cv. Meski, Manzanilla and Picholine) showing circular spots 1 to 10 mm in diameter, slightly depressed and reddish-brown in color, were collected from local markets and orchards located in the regions of Takelsa, Zarzis and Rgueb in Tunisia. Colletotrichum gloeosporioides was isolated from symptomatic fruits and Koch's postulates were fulfilled. This is the first report of Colletotrichum gloeosporioides causing anthracnose of olives in Tunisia. [ABSTRACT FROM AUTHOR]

Olive trees (Olea europaea) cv. Meski having leaves with yellow spots on the upper surface and grey blotches on the lower surface were found in three orchards located in the regions of Takelsa, Testour and Enfidha, central and northern Tunisia. The shoots of the olive trees had also become defoliated indicating a severe attack of a pathogen. Pseudocercospora cladosporioides was isolated from symptomatic leaves and Koch's postulates were fulfilled. This is the first Tunisian report of P. cladosporioides causing Cercospora leaf spot of olive trees. [ABSTRACT FROM AUTHOR]

The purpose of this study was to isolate and identify Rhodococcus spp. strains from almond and pistachio rootstocks and trees in Tunisia. Twenty-eight strains were identified through 16S rDNA and vicA genes amplification and sequencing. Pea bioassay was performed to determine the pathogenicity of the strains. Representative 16S rDNA and vicA sequences of eight strains from pistachio and seven strains from almond were closely related (>98% similarity) to Rhodococcus spp. accessions in GenBank. Phylogenetic analysis based on 16S rDNA sequences revealed that the yellow-colored strains clustered with phytopathogenic Rhodococcusfascians. The red and orange-colored strains were separated into a different group with R. kroppenstedtii and R. corynebacteiroides isolates. Eleven strains affected the pea seedlings' growth and exhibited different levels of virulence. The number of shoots was significantly higher in seedlings inoculated with four Rhodococcus strains, whereas the other three strains caused up to 80% of plant height reduction and reduced root secondary growth compared to non-inoculated pea seedlings. These strains, most of which are epiphytes from asymptomatic hosts, showed strong pathogenicity during pea bioassay and were established endophytically in pea tissues. Ten att and five fas genes were detected in four strains and may represent a novel model of plant pathogenic Rhodococcus virulence. The results of our survey showed that Rhodococcus is present but not prevalent in all visited orchards of almond and pistachio rootstocks and trees. Our surveys complemented the investments being made on ornamental species in Tunisia and unveiled the presence of undocumented plant-associated Rhodococcus spp. on economically important crops. [ABSTRACT FROM AUTHOR]

The genus Rhodococcus contains several species with agricultural, biotechnological and ecological importance. Within this genus, many phyllosphere, rhizosphere and endosphere strains are plant growth promoting bacteria, whereas strains designated as R. fascians are plant pathogens. In this study, we isolated 47 Rhodococcus strains from a range of herbaceous and woody plant species. Phylogenetic analysis based on 16S rDNA, gyr B and alk B genes was used to compare our strains with type strains of Rhodococcus . For most of our strains, sequence similarity of the 16S rDNA, gyr B and alk B regions to type strains ranged from 98-100 %. Results of the concatenated gene sequence comparisons identified 18 strains of R. fascians and three strains of R. kroppenstedtii . The remaining strains were unclassified, and may represent novel species of Rhodococcus . Phylogenetic analysis based on gyr B sequences provided a more precise classification of our strains to species level than 16S rDNA sequences, whereas analysis of alk B sequences was unable to identify strains with orange-coloured colonies to species level.