Effet des extraits de compost sur la croissance mycélienne et l'agressivité du Fusarium oxysporum f. sp. radicis-lycopersici

Effect of compost tea on mycelial growth and disease severity of Fusarium oxysporum f. sp. radicis-lycopersici. Simultaneous addition, on culture media, of Fusarium oxysporum f. sp. radicis-lycopersici and compost teas revealed that the latest induced the inhibition of the mycelial growth of the pathogen. This inhibition, noted after an incubation period of about six days at 25°C, was more important when compost teas were enriched in PDB (Potato Dextrose Broth), where it may reach 70% compared to the control. Transplantation of tomato seedlings, previously inoculated by a conidial suspension of F. oxysporum f. sp. radicis-lycopersici, in a container media (peat, perlite or the mixture of the two substrates) treated by compost teas has signifi cantly reduced Fusarium crown and root rot incidence compared to inoculated and untreated control seedlings. Disease incidence is more reduced when tomato inoculated plants are transplanted in peat treated by compost teas; indeed, these plants donʼt show any wilting and present a vigorous root system and a better vegetative growth

Chemical composition and biological activities assessment of olive fruit volatiles from different varieties grown in Tunisia

Volatile compounds, present in olives, are responsible for the olive fruit flavor and oil aroma, influencing the consumer’s preference. These compounds have a biological activity to fight off pathogens. The aim of this work is to characterize volatiles in pulps and cores of Chemlali, Arbequina and Koroneiki olives, collected from Menzel Mhiri-Kairouan, and to test both the efficiency of these compounds against two bacteria and six phytopathogenic fungal species, by diffusion and dilution methods, and their antioxidants activities. The analyzis of volatiles were determined by GC-FID and GC-MS in three cultivars at the full ripening stage. Thirty five compounds were identified, such us an assortment of phenol, alcohol, hydrocarbon, aldehyde and terpenes derivatives. A high changes in volatiles was noted between cultivars and fruit organs. In fact, the major compounds in the pulps and the cores, of different cultivars, are (E)-2-decenal (46.9%), nonanal (19.6%), 1-hexadecene (16.3%), 7-methyl-1,3,5-cycloheptatriene 7-methyl-1,3,5-cycloheptatriene (15.47%), (E,E)-2,4-decadienal (14.5%) and 1-tetradecene (14.6%). Also, the cores volatiles illustrated more richness in aldehydes than the pulps for all cultivars. Volatile fractions exhibited a moderate to important antibacterial activities against bacteria. However, Arbequina cores volatiles and both Chemlali and Koroneiki pulps volatiles established a moderate to higher activities against tested fungi. The DPPH and ABTS˙⁺ tests demonstrated that the highest antioxidant capacity of volatiles were assigned to Arbequina cores and Koroneiki pulps. The Principal Components Analysis showed a significant relationship between antioxidants and/or antimicrobial properties and the levels of the main volatile compounds (limonene, methyldecane, nonanal, E-2-decenal, camphor, geranic acid, tetradecene, hexadecane, tetradecane) in different fruit organs

Genetic diversity of Fusarium oxysporum populations isolated from tomato plants in Tunisia

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceFusarium crown and root rot of tomato (Lycopersicon esculentum) caused by Fusarium oxysporum f. sp. radicis-lycopersici is a new devastative disease of tomato greenhouse crops in Tunisia. Nothing is known neither about the population of this pathogen in this region, nor about the population of F. oxysporum f. sp. lycopersici the causal agent of Fusarium wilt of tomato. In order to examine the genetic relatedness among the F. oxysporum isolates by intergenic spacer restriction fragment length polymorphism (IGS-RFLP) analysis and to elucidate the origin of the formae specialesradicis-lycopersici in Tunisia by looking for genetic similarity of Tunisians isolates with isolates from a foreign source, the genetic diversity among F. oxysporum f. sp. radicis-lycopersici and F. oxysporum f. sp. lycopersici populations was investigated. A total of 62 isolates of F. oxysporum, obtained from symptomless tomato plants, were characterized using IGS typing and pathogenicity tests on tomato plants. All Fusarium isolates were highly pathogenic on tomato. Fusarium oxysporum f. sp. radicis-lycopersici isolates were separated into five IGS types. From the 53 F. oxysporum f. sp. radicis-lycopersici isolates, 34 isolates have the same IGS types (IGS type 25), and the remaining 19 isolates were distributed into four IGS types. However, the only nine isolates of F. oxysporum f. sp. lycopersici have six different IGS types. This difference of diversity between the two formae speciales suggests that F. oxysporum f. sp. radicis-lycopersici isolates have a foreign origin and may have been accidentally introduced into Tunisia

Involvement of lipopeptide antibiotics and chitinase genes and induction of host defense in suppression of Fusarium wilt by endophytic Bacillus spp. in tomato

Five endophytic Bacillus spp. isolated from surface-sterilized stem tissues of wild Solanaceous species, i.e. Datura metel, Solanum nigrum and S. elaeagnifolium, were screened for their in vitro and in vivo antagonistic potential against Fusarium oxysporum f. sp. lycopersici (FOL). Pathogen sporulation was totally suppressed by these five strains and its mycelial growth was significantly decreased using bacterial whole-cell suspensions and cell-free culture filtrates. Extracellular metabolites remained effective after heating at 50–100 °C with a decline in activity with treatments involving temperatures at 100 °C, proteinase K addition, and pH adjustments to 2 or 12. Chitinase and lipopeptide antibiotic genes were detected using PCR amplification. The five strains produced salicylic acid when grown in succinate medium, with the greatest production exhibited by B. subtilis str. SV41. In planta application of Bacillus spp. cell-free culture filtrates and whole-cell suspensions significantly decreased Fusarium wilt severity by 87–100% and enhanced tomato growth by 38–80%, compared to FOL-inoculated and untreated controls. The two Bacillus strains exhibiting the strongest decrease in Fusarium wilt severity (B. subtilis str. SV41 and B. amyloliquefaciens subsp. plantarum str. SV65) were further evaluated for their ability to induce systemic resistance (ISR) in FOL-infected and uninfected tomato plants. Using quantitative RT-PCR, the expression of the acidic PR-1 and PR-3 genes as well as the lipoxygenase (LOXD) gene were significantly induced in plants treated with B. amyloliquefaciens subsp. plantarum str. SV65. This effect was observed in both FOL-inoculated and uninoculated plants. © 201

A putative endophytic Bacillus cereus str. S42 from Nicotiana glauca for biocontrol of Fusarium wilt disease in tomato and gas chromatography-mass spectrometry analysis of its chloroform extract

A putative endophytic Bacillus cereus str. S42 (KP993206), recovered from surface-sterilised stems of Nicotiana glauca was assessed in vitro and in vivo for its antifungal potential towards Fusarium oxysporum f. sp. lycopersici (FOL). Pathogen sporulation was significantly inhibited by B. cereus str. S42. FOL mycelial growth was reduced using its whole-cell suspensions, cell-free culture supernatant and chloroform extract. Its extracellular metabolites remained effective after heating at 50–100 °C with a decline in their activity was observed beyond 100 °C, when added with proteinase K and/or after pH adjustment to 2 and 12. Chitinase gene was detected using PCR amplification. Gas chromatography–mass spectrometry analysis of its chloroform extract matched phthalic acid, dibutyl ester with high level of similarity. B. cereus str. S42 cell-free culture supernatant and whole-cell suspensions had significantly suppressed Fusarium wilt severity by 87–96% and enhanced tomato growth by 39–79% compared to FOL-inoculated and untreated control. © 2016 Informa UK Limited, trading as Taylor & Francis Group

Occurrence, Characterization and Pathogenicity Test of the Fungi, Aspergillus flavus and Fusarium oxysporum Isolated from Cadavers of Scolytus amygdale Guerin-Meneville (Coleoptera: Curculionidae: Scolytinae)

Natural mortality of the almond bark beetle, Scolytus amygdali Guerin-Meneville (Coleoptera: Curculionidae: Scolytinae) was studied during its spring generation under the bark of infested almond tree branches in Tunisia. Dead larvae and adults of the beetle were collected from the field and analyzed under the laboratory conditions. Two main fungal isolates were obtained from the cadavers of S. amygdali individuals,identified using morphological and molecular tools, as Aspergillus flavus and Fusarium oxysporum. In preliminary studies conducted under laboratory conditions, species of Aspergillus and Fusarium fungi were reported virulent at the concentrations of (0.4 x 10(7) conidia/ml) to S. amygdali. In order to test the pathogencity of the two isolated fungal species, similar concentrations were applied on larvae and adults of healthy S. amygdale individuals. Both fungi were found significantly virulent immediately after 24h under laboratory conditions. Further investigations for their suitability as biocontrol agents in the field are required

Asterisulphoxide and asterisulphone: two new antibacterial and antifungal metabolites from the Tunisian <i>Asteriscus maritimus</i> (L.) Less

<div><p>Two new sulphur-containing metabolites, asterisulphoxide <b>1</b> and asterisulphone <b>2</b>, together with six known compounds, coniferaldehyde <b>4</b>, 4-hydroxy-2-methoxybenzaldehyde <b>3</b>, methylcaffeate <b>5</b>, isobutyrate 10-isobutyryloxy-8,9-epoxythymyle <b>6</b>, 8,9-dihydroxy-10-isobutyryloxythymol <b>7</b> and 8-hydroxy-9,14-diisobutyryloxythymol <b>8</b>, were isolated from <i>Asteriscus maritimus</i> roots. Their structures were elucidated on the basis of spectroscopic evidence and comparison with authentic samples. Compounds <b>1</b>–<b>8</b> were assessed for their <i>in vitro</i> antibacterial activity against <i>Pseudomonas aureofasciens</i>, <i>Burkholderia glathei</i>, <i>Bacillus pumilus</i> and their antifungal effects against <i>Aspergillus flavus</i>, <i>Aspergillus</i><i> niger</i>, <i>Penicillium digitatum</i>, <i>Botrytis cinerea</i> and <i>Fusarium oxysporum</i> f. sp. <i>lycopersici,</i> using the disc diffusion method (20 μL/disc). A remarkable inhibition zone 10–15 mm of the growth of the bacterial and fungal agents was observed. The obtained results suggest that the isolated compounds could be promising abiotic antimicrobial agents.</p></div

Occurrence, Characterization and Pathogenicity Test of the Fungi, Aspergillus flavus and Fusarium oxysporum Isolated from Cadavers of Scolytus amygdale Guerin-Meneville (Coleoptera: Curculionidae: Scolytinae)

Natural mortality of the almond bark beetle, Scolytus amygdali Guerin-Meneville (Coleoptera: Curculionidae: Scolytinae) was studied during its spring generation under the bark of infested almond tree branches in Tunisia. Dead larvae and adults of the beetle were collected from the field and analyzed under the laboratory conditions. Two main fungal isolates were obtained from the cadavers of S. amygdali individuals,identified using morphological and molecular tools, as Aspergillus flavus and Fusarium oxysporum. In preliminary studies conducted under laboratory conditions, species of Aspergillus and Fusarium fungi were reported virulent at the concentrations of (0.4 x 107 conidia/ml) to S. amygdali. In order to test the pathogencity of the two isolated fungal species, similar concentrations were applied on larvae and adults of healthy S. amygdale individuals. Both fungi were found significantly virulent immediately after 24h under laboratory conditions. Further investigations for their suitability as biocontrol agents in the field are required