Samia Gargouri

Trichothecene chemotypes of Fusarium culmorum infecting wheat in Tunisia.

Fusarium culmorum is a major pathogen associated with Fusarium head blight (FHB) of wheat in Tunisia. It may cause yield loss or produce mycotoxins in the grain. The objectives of the present study were threefold: to evaluate by PCR assays the type of mycotoxins produced by 100 F. culmorum isolates recovered from different regions in Northern Tunisia, to determine the amount of mycotoxin production by HPLC analysis, and to analyse for correlations between the amount of mycotoxin produced and the aggressiveness of isolates. PCR assays of Tri5, Tri7, Tri13, and Tri3 were used to predict whether these isolates could produce nivalenol, 3-acetyl-deoxynivalenol, or 15-acetyl-deoxynivalenol. Two of the isolates were predicted to produce NIV, whereas the others were predicted to produce 3-AcDON. Trichothecene production was confirmed and quantified by high pressure liquid chromatography (HPLC) in 28 isolates, after growth on wheat grains, and in a liquid Mycotoxin Synthetic medium (MS). All strains produced DON/3-AcDON at detectable levels ranging from 21 microg/g to 11.000 microg/g of dry biomass on MS medium and from 10 microg/g to 610 microg/g on wheat grain. The evaluation of the relationship between 3-AcDON production and aggressiveness of 17 strains revealed a significant difference in aggressiveness among the isolates. Moreover, only a significant correlation was revealed between aggressiveness and the amount of 3-AcDON produced on MS medium (r=0.36). Chemotyping of F. culmorum isolates is reported for the first time for isolates from Tunisia, and highlights the important potential of F. culmorum to contaminate wheat with 3-AcDON trichothecenes.

Chemical composition, phytotoxic and antifungal activities of Pinus pinea essential oil

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Tunisian Pinus pinea Linn. was analyzed by GC and GC/MS. Sixty-six compounds were identified, representing 98.5% of total oil, which was found to be rich in monoterpene hydrocarbons (73.1%) particularly limonene (54.1%), α-pinene (7.7%), and β-pinene (3.4%). The yield and the physico-chemical properties were determined. Results of the antifungal activity study by in vitro contact assay showed that P. pinea oil significantly inhibited the growth of ten plant pathogenic fungi. Moreover, herbicidal properties of the oil, tested on Sinapis arvensis L., Lolium rigidum Gaud., and Raphanus raphanistrum L., indicated that the oil completely inhibited the seed germination at a high concentration, while at low doses the oil acted by decreasing and delaying the germination and inhibiting the seedling growth of all tested weeds unlike the commercial herbicide. Our results showed that P. pinea essential oil could be valorized as bioproduct for biocontrol of weeds and fungal plant diseases.

Genetic variability and population structure of the wheat foot rot fungus, Fusarium culmorum, in Tunisia

The random amplified polymorphic DNA (RAPD) method was used to investigate the genetic variability and population structure of Fusarium culmorum isolated from wheat stem bases. A total of 108 isolates, representing seven geographically distinct populations, was collected from five climatic regions in Tunisia. Pseudo-allelic frequencies were estimated at each of the 25 putative RAPD loci analyzed by scoring for the presence or absence of amplified fragments; 92 haplotypes were found among the 108 strains. The analysis of the population structure did not reveal any trend with regard to geographic origin. Total gene diversity (HT* = 0.318) was mostly attributable to diversity within populations (HS* = 0.308). Analysis of molecular variance confirmed that most of the genetic variability was within populations. Genetic differentiation among populations was low to moderate (GST* ranged from 0 to 0.190 and averaged 0.041 over all loci). Cluster analysis with UPGMA using genetic distances did not reveal any spatial clustering of the isolates collected from the different geographic regions. Based on these results, we conclude that the F. culmorum isolates recovered from different regions in Tunisia might be part of a single population pool.

Chemical composition, physico-chemical properties, antifungal and herbicidal activities of Pinus halepensis Miller essential oils

The chemical composition, physico-chemical properties, and antifungal and herbicidal activities of essential oils obtained by hydrodistillation from needles, stems and cones of Pinus halepensis Miller were investigated. The chemical composition analysed by GC and GC/MS varied significantly among organs. Among the 67 identified components, α-pinene (63% and 51.7%, respectively, in stems and cones) and (Z)-caryophyllene (33.9% in needles) were found to be the major ones. Moreover, it was found that chemical composition of essential oils extracted from different organs of P. halepensis Miller growing in Tunisia showed noteworthy differences with the same species cultivated in Algeria, Morocco, Greece and Italy based on a comparison with published results. In addition, the physico-chemical properties of essential oils from different organs of P. halepensis were analysed. The analysis of the refraction index, density and acid index of different oil samples showed a weak variability among organs. The in vitro antifungal activity of the essential oil samples evaluated against 10 cultivated crop fungi was found to be low, probably due to the low level of oxygenated compounds in P. halepensis oils. In contrast, the herbicidal activity investigated towards three common weeds in Tunisian cereal crops was very strong and seed germination was inhibited at 2 μl ml− 1. Thus, P. halepensis essential oil appears to have more value as a bioherbicide than as a biofungicide.

Comparative study of two coniferous species (Pinus pinaster Aiton and Cupressus sempervirens L. var. dupreziana [A. Camus] Silba) essential oils: chemical composition and biological activity

Maritime pine ( Pinus pinaster Aiton) and Saharan cypress ( Cupressus sempervirens L. var. dupreziana [A. Camus] Silba) are two cone-bearing seed coniferous woody plants. The chemical composition of their essential oils, isolated from needles and leaves by hydrodistillation, was analyzed with gas chromatography (GC) and gas chromatography mass spectrometry (GC/MS). A total of 66 and 28 compounds were identified, which represented 99.5% and 98.9% of total pine and cypress oils, respectively. Pinus pinaster oil was found to be rich in α-pinene (31.4%), (Z)-caryophyllene (28%), and α-humulene (6.7%); it was characterized by relatively high amounts of monoterpene and sesquiterpene hydrocarbons (44.5% and 46.3%, respectively). The major components identified in cypress oil were manoyl oxide (34.7%), α-pinene (31.8%), α-humulene (9%), and 6-3-carene (8.7%). Results of in vitro antifungal test assays showed that both oils significantly inhibit the growth of 10 plant pathogenic fungi. Herbicidal effects of the oils on seed germination, seed vigor, and seedling growth of three common crop weeds Sinapis arvensis L., Phalaris paradoxa L., and Raphanus raphanistrum L. were also determined; the oils completely inhibited seed germination and seedling growth of all the weeds.

Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils.

The chemical composition, and phytotoxic and antifungal activities of the essential oils isolated by using hydrodistillation from the aerial parts of Tunisian rue were evaluated. Significant variations were observed among harvest periods. The analysis of the chemical composition by gas chromatography/mass spectrometry showed that 2-undecanone (33.4–49.8%), 2-heptanol acetate (13.5–15.4%) and α-pinene (9.8–11.9%) were the main components. The antifungal ability of rue essential oils was tested by using disc agar diffusion against ten plant pathogenic fungi. A high antifungal activity was observed for the essential oil isolated at flowering developmental phase. Furthermore, rue essential oils showed high level of herbicidal activity against several weeds.

Allelopathic effects of essential oils of Pinus halepensis Miller: chemical composition and study of their antifungal and herbicidal activities

The chemical composition, phytotoxic and antifungal activities of the essential oils isolated by hydrodistillation from the needles of Tunisian Aleppo pine harvested from different provenances were evaluated. The chemical composition analysed by gas chromatography/mass spectrometry (GC/MS) revealed variability among provenances displaying interesting chemotypes, (Z)-caryophyllene (16.16–28.9%), β-myrcene (8.5–22.9%), α-pinene (11.7–13.14%), β-pinene (3.13–11.8%), bicyclogermacrene (5.2–12.37%), α-terpinolene (8.11–11.01%) and α-humulene (2.85–5.2%), which were the main components in the oil. Antifungal ability of Aleppo pine oils was tested by disc agar diffusion against 10 phytopathogenic fungi. Weak antifungal activity was observed for the essential oils isolated. Furthermore, in contrast, the herbicidal activity investigated for three common weeds in Tunisian cereal crops was very strong and seed germination was inhibited at a low concentration and their herbicidal effects were higher than those of a commercial herbicide.

Propriétés antifongiques des huiles essentielles de Biota orientalis L.

RésuméLa composition chimique des huiles essentielles d’aiguilles et de cônes de Biota orientalis L. extraites par hydrodistillation a été analysée par chromatographie gazeuse associée à une détection à ionisation de flamme (CG-DIF) et par chromatographie gazeuse couplée à la spectrométrie de masse (CG-SM). Vingt et un composés ont été identifiés chez l’huile essentielle de Biota orientalis, qui s’est avérée particulièrement riche en monoterpènes hydrocarbonés. Des différences quantitatives principalement ont été observées entre les aiguilles et les cônes, quoiqu’ils affichent le même chémotype. Pour les deux huiles, α-pinène (67 et 47 % respectivement chez les cônes et les aiguilles), β-phellandrène (5,1 et 10,9 %) et α-cédrol (4,6 et 7,5 %) constituent les composés majeurs identifiés. L’étude de leur activité antifongique vis-à-vis d’une dizaine de champignons phytopathogènes a révélé des propriétés intéressantes qui pourraient être valorisées en tant que biofongicide.AbstractThe chemical composition of essential oils isolated by hydrodistillation from needles and cones of Biota orientalis L. was analyzed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Twenty one compounds were identified in Biota orientalis essential oil which appeared to be rich in monoterpene hydrocarbons. Quantitative differences mainly, between cone and needle oils, were observed, although they displayed the same chemotype. For both oils, α-pinene (67 and 47% respectively in cones and needles), β-phellandrene (5.1 and 10.9%) and α-cedrol (4.6 and 7.5%) were the major constituents. The study of their antifungal activity towards ten plants pathogenic fungi revealed interesting properties that could be applied as biofungicide.

Activity antifungal of the essential oils; aqueous and ethanol extracts from Citrus aurantium L.

Our study is about the essential oil of Citrus aurantium L. in Tunisia and its plant extract. The yield of this essential oil is 0, 56% but the yield of the extract of plant was 17.1% for the aqueous extract ant 18.3% for the ethanolic extract. The analysis of chemical composition by using GC and GC/MS showed the essential oil of C. aurantium L. species to be rich in monoterpenes such as α-terpineol, lianolyl acetate, linalool and limonene. The antifungal activity of this oil showed us an inhibition of the germination of mushrooms, in the same way we could note that the biologic activities are generally assigned to the chemotypes high content in oxygenated monoterpene.

Chemical Composition and Biological Activities of Tunisian Cupressus arizonica Greene Essential Oils

The chemical composition of the essential oils obtained by hydrodistillation of leaves, stems, and female cones of Cupressus arizonica Greene, grown in Tunisia, was studied by GC‐FID and GC/MS analyses. Altogether, 62 compounds were identified, 62 in the leaf oil, 19 in the cone oil, and 24 in the stem oil. The cone and stem oils were mainly composed by monoterpene hydrocarbons (96.6 and 85.2%, resp.). In the leaf oil, the total sesquiterpene fraction constituted 36.1% and that of the monoterpene hydrocarbons 33.8% of the total oil composition. The three oils were evaluated for their in vitro herbicidal activity by determining their influence on the germination and the shoot and root growth of the four weed species Sinapis arvensis L., Lolium rigidum Gaudin, Trifolium campestre Schreb., and Phalaris canariensis L. At the highest doses tested (0.8 and 1.0 mg/ml), the leaf essential oil inhibited either totally or almost completely the seed germination and the shoot and root growth of S. arvensis and T. campestre. The oils were also tested for their antifungal activity; however, their effects on the fungal growth were statistically not significant.