Search

In Tunisia, the increasing pharmacological demand for spontaneous capers is actually leading to progressive forest overexploitation and genetic erosion of the species that is actually represented by scattered populations. Therefore, inventories with emphasis on the characterization, management and conservation of this medicinal plant are becoming a great need. In this work, genetic and phylogenetic criteria based on isozyme markers were used for the prioritization of spontaneous Capparis spinosa L. populations for conservation according to Vane-Wright and collaborators taxic method. Enzymatic loci varied in their ability to detect variation and population analyses indicated that most of the variation is partitioned between rather than within populations. Fst , gene flow values, PCA and cluster analysis also revealed significant differentiation between all populations. When combing phylogenetic and genetic criteria we were able to prioritize some of the populations for conservation. Therefore, the standardization and the summatory of all indices indicated that the populations Nebeur, Nahli and Dyr rank as a priority for conservation. So far, results of the present study appear to justify the in situ conservation strategy, where core areas completely free from perturbation would be defined for the populations with the highest priority for conservation, with the populations presenting unique alleles. This would guarantee the maintenance of most of the species’ genetic variation. The ex situ conservation management strategy would imply the setting up of specialized nurseries and national collections that are still missing in the country to counteract population fragmentation, demographic loss and genetic erosion threatening such spontaneous populations. [ABSTRACT FROM AUTHOR]

Highlights: [•] We assessed population structure in Tunisian Vitis sylvestris using SSRs. [•] Genetic and demographic data highlighted high extinction level within this flora. [•] Various conservation plans were suggested for best management of grapevine. [Copyright &y& Elsevier]

Abstract: Cereals contamination with mycotoxigenic species of Fusarium is considered as a major source of trichothecenes and other mycotoxin groups which cause severe yield losses and serious diseases in human and animal health. Early detection of Fusarium species could be for a great interest to prevent mycotoxin contaminating agro-products. We have established for the first time a direct polymerase chain reaction (DPCR) protocol to detect contamination with trichothecene-producing F. culmorum in wheat samples. We have successfully amplified fungal genomic DNA using specific primers targeting the trichothecenes biosynthetic Tri5 gene. We further investigated a versatile multiplex-DPCR on the basis of Tri5 gene and IGS (Intergenic Spacer of rDNA) specific sequence of F. culmorum for its identification at specie level and prediction of its potential trichothecenes production simultaneously. Our protocol allowed amplification directly from crude templates with no need of DNA extraction or purification methods and did not require any culture-based approach. These DPCR assays represent a reliable tool for high throughput screening, detection and rapid characterization of mycotoxigenic isolates as well as diverse applications in food industry. [Copyright &y& Elsevier]

For many years the needs of consumers, farmers and the seed industry have changed significantly. To meet these expectations, investments in research on durum wheat varieties are needed. In this context, five modern varieties of durum wheat (Karim, Razzek, Nasr, Khiar and Om Rabiaa), obtained through a selection program, harvested in northern Tunisia, have been investigated, deepening their technological and nutritional characteristics. The results obtained were evaluated using chemometric tools to visualize the interaction of these results with their calorific values. All wheat samples examined are characterized by low average grain glassiness values (0.67–10.65%), fatty acidity (≈0.05%) and moisture (≈10%), and high average values of thousandths weight (45.04–53.58 g), weight (≈84 kg h L−1) and monounsaturated fatty acids (20.34–25.62%). They also have appreciable quantities of gluten (from 26.49 to 42.22% of dry matter) and total protein (from 12.64 to 15.17% of dry matter) with an energy value of about 340 Kcal/100 g. According to UPLC-ESI-QTOF-MS analysis, dihydroferulic acid was shown to be the most abundant phenolic compound detected in all varieties, constituting approximately 30–40% of the phenolic compounds. The wheat variety strongly affects almost all technological and chemical parameters. Chemometric tools have allowed us to highlight the differences in the different varieties of wheat. In particular, the linear projections of the nutritional and technological characteristics of durum wheat were differentiated according to their calorific value, whereas the use of a heatmap was useful to create a hierarchical cluster of the wheat features. • Tunisian durum wheat has an ideal nutritional and technological quality. • Chemometric tools were effective in distinguishing wheat varieties. • Wheat variety strongly influences technological & chemical parameters. [ABSTRACT FROM AUTHOR]

The constitutive expression of a Vitis vinifera dehydrin ( DHN ) of the YSK 2 type ( VvDhn ) allowed for a more vigorous growth in transgenic tobacco plants than in wild-type (WT). In vitro , a very distinct germination kinetics and root development profile was observed both under optimal and stress conditions (control, mannitol, NaCl). Transgenic lines outperformed WT in germination success and precocity and root length. Furthermore, transgenic lines were able to germinate under 300 mM mannitol. Adult tobacco plants expressing VvDhn also displayed improved tolerance to both drought and salt stresses. The VvDhn lines under these constraints were significantly better than WT in terms of biomass and leaf number. Moreover, higher capacities to recover from drought were revealed. However, the major effect the VvDhn over-expression was observed under non limiting conditions. VvDhn interfered with the development program leading to higher biomass production (leaf, shoot and root) and to the production of higher number of leaves. The VvDhn gene show great promise for grapevine genetic improvement to drought and salinity tolerance. VvDhn gene can be used to screen and/or design for new grapevine rootstocks that together with viticultural management programs has the potential to cope successfully with a more adverse and unpredictable climate, which is highly demand by community. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cladodes from prickly O. ficus indica cultivars have a thick cracked epicuticular wax layer with an amorphous structure. [•] Spineless O. ficus indica cultivars have a less thick waxy layer with a rough crystalloid structure on their cladodes. [•] Persistent spines present a compact arrangement of oblong epidermal cells with a rough granular structure and filamentous prints. [•] Deciduous spines have a broken transversely fissured epidermis covering a parallel arrangement of fibres. [Copyright &y& Elsevier]

Abstract: This paper summarizes the results of a large study on the occurrence of ochratoxigenic fungi and Ochratoxin A from wine and table grapes in Tunisia. Our results revealed that Aspergillus section Nigri were the unique potential OTA producing fungi isolated from grapes. Isolates belonging to Aspergillus niger aggregate were the most abundant species followed by Aspergillus carbonarius isolates, then uniseriate aspergilli. A. carbonarius presented the highest percentage of OTA-positive strains (97%) whereas only 3% of A. niger aggregate isolates were OTA positive. Grapes were analysed for their OTA content and 58% of them contained detectable levels of OTA, between 0.05 and 5.85 μg/l. Only 4 samples out of 39 exceeded the OTA limit of 2 μg/l fixed by the EU for wine and grape juices. The most contaminated grapes were those from Raf–Raf region located in the North-Est and characterized by a humid climate. Grapes from the Regueb region, characterized by an arid climate, were rarely contaminated. Furthermore, A. carbonarius, which is the main OTA producer fungi on grapes, was rarely isolated in Regueb. [Copyright &y& Elsevier]

Abstract: In this study, 51 samples of cereals (wheat, Barley, maize and Sorghum) and by-products (mainly pasta and couscous) purchased from Tunisian supermarkets were examined for contamination with the emerging Fusarium mycotoxins: Enniatins ENs (EN A, EN A1, EN B and EN B1), beauvericin (BEA) and fusaproliferin (FUS). The extraction of the samples was performed with methanol using an Ultra-turrax homogenizer. Mycotoxins were analyzed with a liquid chromatography (LC) coupled to a diode array detector (DAD). The frequencies of contamination of total samples with ENs were 96%. EN A1 was the most common EN found with the highest prevalence of 92.1%, levels ranged between 11.1 and 480 mg/kg. EN B was evidenced in 35 samples and levels ranged from 1.5 to 295 mg/kg. EN B1 was detected in 20 samples (39.2%) and levels varied from 4.8 to 120.1 mg/kg and EN A was detected in 14 samples with contamination levels ranging between 19.6 and 121.3 mg/kg. The maximum concentration of total ENs in a single sample was 683.9 mg/kg (sorghum). The analytical results also showed that all the analyzed samples were free of BEA and FUS. The present work is the first one ever drafted on the presence of the emerging Fusarium mycotoxins in Tunisian cereals and derived products. [Copyright &y& Elsevier]

Abstract: Salt stress adversely affects the growth of grapevine plants. In order to understand the molecular basis of salt stress response in grapevine plants, suppression subtractive hybridization (SSH) and microarray based screening approaches were combined. Two leaf-specific subtractive cDNA libraries were constructed from grapevine plants subjected to a moderate, incremental salt stress treatment. SSH were performed 6h and 24h after NaCl peaked at 100mM using cDNAs prepared from leaves of a salt tolerant cultivar (Razegui) as testers and cDNAs from unstressed leaves as drivers. Then, a pre-screened subset of cDNA clones from these SSH libraries were used to construct a Vitis vinifera cDNA array, in order to verify the expression changes of the genes upon salt treatment. Expression profiles were compared between the salt tolerant and a susceptible cultivar (Syrah) under both control conditions and after salt stress treatment. Seven cDNA clones were identified which were up-regulated by salt stress in two independent growth experiments and confirmed by RNA blot analysis. The transcript expression patterns of the selected genes differed between the contrasting grapevine cultivars tested with respect to stress-regulation. The possible relationship of individual cDNAs with salinity tolerance mechanisms is discussed. [Copyright &y& Elsevier]

Abstract: The effect of three alternating temperatures cycles (20/30, 20/37 and 25/42°C) and photoperiod on growth and Ochratoxin A (OTA) production of six isolates of Aspergillus carbonarius on synthetic nutrient medium were investigated. The different temperature regimes affected significantly both the mycelial growth and the OTA production. The best growth and OTA production were recorded at 20/30°C. The isolates from the region of Baddar produced the highest OTA yields. A 24h light cycle generally enhanced the growth of A. carbonarius. Growth rates cycles of 11h/13h light/darkness and 24h darkness were often similar for individual isolates, such conditions enhanced OTA production in two of the six isolates tested. [Copyright &y& Elsevier]

Summary: Salt stress is one of the major abiotic stresses in agriculture worldwide, especially in the Mediterranean area. We report here a proteomic approach to investigate the salt stress-responsive proteins in grapevine (Vitis vinifera). Two-dimensional electrophoresis (2-DE) was used to analyze the proteome of the salt-tolerant Tunisian grapevine cultivar Razegui, subjected to a supply of 100mm NaCl over 15d. Analysis of 2-DE gels derived from stressed plants revealed more than 800 reproducibly detected protein spots, with 48 proteins displaying a differential expression pattern, including 32 up-regulated, 9 down-regulated and 7 new protein spots induced after salt treatment. The presence of stress-responsive proteins in the different plant organs suggests that salt spreads systemically. Edman degradation analysis and database searching aided us in identifying a major protein GP. Database analysis revealed that this peptide has a 98% sequence similarity with a pathogenesis-related (PR) protein 10 (V. vinifera). A full-length cDNA encoding the GP protein was isolated from grapevine salt-stressed leaves and sequenced. The predicted protein contained 158 amino acids and showed 98% identity with PR10 protein of of V. vinifera (accession no. Cac16165). [Copyright &y& Elsevier]

The current study assesses the natural occurrence of mycotoxins and fungal metabolites in Tunisian Pearl millet. Investigations using a multi-mycotoxin liquid chromatography/electrospray ionization-tandem mass spectrometric (LC/ESI–MS/MS) method were carried out on a total of 220 pearl millet samples collected from farmers (n = 144) located in four different agroecological zones in Tunisia and from retail shops (n = 76). Results revealed fifty-seven regulated and emerging metabolites contaminating 91.4% of grain samples. Among major mycotoxins, both aflatoxin B1 (AFB1) and ochratoxin A (OTA) were the most prevalent at rate of 8.6% each and occurring at an average level of 106 and 69.4 μg/kg, respectively. All positives samples were significantly exceeding the European thresholds (5 and 3 μg/kg, respectively). Lower incidence (5.9%) of Zearalenone (ZEA) contaminated samples at levels below the authorized limits (100 μg/kg) was recorded. Pearl millet grains from the south coastal zone (CT.S) had significantly the highest mean AFB1 contamination (p < 0.05). Meanwhile, OTA was encountered only in CT.S zone. Furthermore, commercial samples showed higher OTA and ZEA mean concentrations than farmers samples (p < 0.05). As regards emerging mycotoxins, Fusarium mycotoxins including beauvericin (BEA), equisetin (EQUS), monoacetoxyscirpenol (MAS) and diacetoxyscirpenol (DAS) were detected in 43.2%, 43.2%, 11.4% and 10.5% of positive samples, respectively. Furthermore, 12.7%, 50.9%, 53.2% and 14.1% of grains were contaminated with Alternaria mycotoxins namely alternariol (AOH), alternariolmonomethyl ether (AME), tentoxin (TEN) and tenuazonic acid (TA), respectively. The majority of emerging Fusarium and Alternaria mycotoxins mean levels were significantly higher in grains from north coastal area (p < 0.01). The present study highlighted a wide range of mycotoxins in Tunisian pearl millet with a different mycotoxin patterns within the agroecological zones. • Analysis of a comprehensive range of mycotoxins in pearl millet by LC/MS/MS. • 201/220 pearl millet samples were detected positive for at least one metabolite. • AFB1 and OTA positive samples were highly contaminated in the coastal south zone. • Emerging Fusarium and Alternaria mycotoxins were higher in the coastal north zone. [ABSTRACT FROM AUTHOR]