Effectiveness of mating disruption with TUTATEC® dispensers against Tuta absoluta (Lepidoptera: Gelechiidae) in heated greenhouses in southern Tunisia

Phytoparasitica - Tomato production in geothermal greenhouses in Tunisia showed remarkable growth during the last decade and has been considered an important economic sector within the Tunisian...     

Transmission Efficiency of <Emphasis Type="Italic">Potato Leafroll Virus</Emphasis> by Four Potato Colonizing Aphid Species in Tunisian Potato Fields

This study investigated the transmission efficiency of Potato leafroll virus (PLRV) by four potato colonizing aphid species, Myzus persicae, Macrosiphum euphorbiae, Aphis gossypii and Aphis fabae, reported from leaves and yellow water trap. Physalis floridana was used as a test plant for virus transmission. DAS-ELISA was used for virus screening of samples as well as virus detection on the test plant after transmission experiment. A 2-h period was sufficient for the tested aphids to acquire PLRV virions. However, a difference in the transmission potential occurred according to the aphid species. The highest potential was recorded for M. persicae and M. euphorbiae, at 90 and 80%, respectively. For the first time, the study revealed the PLRV transmission efficiency of A. fabae, estimated at 50%. The lowest potential rate of 30% was recorded for A. gossypii. This study highlights the PLRV transmission capacities of four potato colonizing aphids suspected to play a key role in the spread of PLRV in potato seed production sites.     

Chemical composition of Eucalyptus erythrocorys essential oils and evaluation of their herbicidal and antifungal activities

The chemical composition of essential oil isolated by hydrodistillation from the leaves of Tunisian Eucalyptus erythrocorys Linn. was analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC/MS). Fifteen compounds were identified, representing 97 % of total oil, which was found to be rich in oxygenated monoterpenes (66.7 %), particularly in 1,8-cineole (54.8 %). The yield and the physico-chemical properties of oil were determined. The study of antifungal activity revealed that E. erythrocorys essential oil significantly inhibited the growth of five plant pathogenic fungi especially Bipolaris sorikiniana and Botritys cinerea. Moreover, herbicidal properties of the oil, tested on Sinapis arvensis L. and Phalaris canariensis L. indicated that the E. erythrocorys oil completely inhibited the seed germination at high concentration (1.5 μl/ml), while at low doses (0.25, 0.5, 0.75, 1 μl/ml) the oil acted by decreasing and delaying the germination and inhibiting the seedling growth of all tested weeds.     

Gonadosomatic index and gonad histopathology of Gobius niger (Gobiidea, Teleost) from Bizerta lagoon (Tunisia): Evidence of reproduction disturbance

To evaluate the effect of anthropogenic pollution on fish reproduction in Bizerta lagoon, one of the largest Tunisian lagoons subjected to various anthropogenic and industrial pressures, the gonadosomatic index (GSI) and gonad histology of mature black goby (Gobius niger) were studied. Fish were collected during the breeding seasons from six stations differently impacted and in one reference station located at the seaward entrance of Ghar el Melh (GH) lagoon. In both sexes, we detected the presence of an overall weaker GSI in Bizerta lagoon than in control fish. These GSI alterations were accompanied by histopathological changes. In females, no significant differences in oocyte size were found across all the sample sites. However, a higher incidence of oocyte lesions (atretic oocytes, cytoplasmic retraction and karyoplasmic cluping) was found in stations located near agricultural activity zones. Histological observation of the testes revealed, as well, abnormalities in Bizerta lagoon fish: germ cells syncytium, vacuolated germ cells, melano-macrophage center and increase of gaps in the interstitium between lobules were detected with a high prevalence in stations influenced by industrial and/or urban activities. In addition, association between gonad fish histopathology and the presence of organic pollutants (DTT, PAHs and organotins) in sediment was noted. These results suggest that the chemical pollution in this lagoon may have adversely affected the gonad development of fish. In conclusion, this study is the first histological evidence of reproduction disturbance related to pollution pressure in a fish species inhabiting Bizerta lagoon. The high levels of gonad histopathology recorded raise concerns about the long-term health of fish populations in this lagoon.     

Seasonal Variations in Proximate and Fatty Acid Composition of Viscera of Sardinella aurita,Sarpa salpa,and Sepia officinalis from Tunisia

Seasonal variations of the proximate composition and fatty acid profiles in viscera from Sardinella aurita, Sarpa salpa, and Sepia officinalis were studied. Significant seasonal variations were observed in the amounts of moisture, lipid, protein, and ash between species. Viscera protein content undergoes large fluctuations. This tendency is different from results observed for the edible parts or for the whole body of many marine species. Ash content also showed significant differences. Lipid contents varied with seasons, in a proportionally inverse manner to water contents. Fatty acid composition showed significant differences from October to December. Interestingly, the highest total omega-3 contents were comparable to many commercial marine fish oils.     

Antibacterial Polyketides from the Marine Alga-Derived Endophitic Streptomyces sundarbansensis: A Study on Hydroxypyrone Tautomerism

Polyketide 13 [=2-hydroxy-5-((6-hydroxy-4-oxo-4H-pyran-2-yl)methyl)-2-propylchroman-4-one] and three related known compounds 7, 9 and 11 were obtained and structurally characterized from Streptomyces sundarbansensis strain, an endophytic actinomycete isolated from the Algerian marine brown algae Fucus sp. Compound 13 was obtained as the major metabolite from optimized culture conditions, by using Agar state fermentation. Due to tautomeric equilibrium, 13 in CD₃OD solution was able to incorporate five deuterium atoms, as deduced by NMR and ESI-MS/MS analysis. The 2-hydroxy-γ-pyrone form was established for these metabolites based on the comparison of their experimental IR spectra with the DFT calculated ones, for both the corresponding 4-hydroxy-α-pyrone and 2-hydroxy-γ-pyrone forms. During antibacterial evaluation, compound 13 stood out as the most active of the series, showing a selective activity against the gram positive pathogenic methicillin-resistant S. aureus (MRSA, MIC = 6 μΜ), with a bacteriostatic effect.     

Effect of growth stage on the content and composition of the essential oil and phenolic fraction of sweet marjoram (Origanum majorana L.)

The variation in the content and composition of Origanum majorana L. essential oil has been studied. Plant material has been harvested at four phenological stages (early vegetative, late vegetative, budding and full-flowering). Essential oil yield varied from 0.04 to 0.09% reached during the full-flowering stage. Analysis of the essential oils by GC and GC/MS revealed the presence of 38 components represented mainly by oxygenated monoterpenes (64.01–71.4%), monoterpene hydrocarbons (21.73–29.92%) and sesquiterpene hydrocarbons (1.47–4.05%). The main components were terpinen-4-ol (29.13–32.57%), cis-sabinene hydrate (19.9–29.27%), trans-sabinene hydrate (3.5–11.61%), γ-terpinene (2.11–8.20%), bornyl acetate (1.52–2.94%) and linalool (1.05–1.39%). On the other hand, phenolic contents varied from 2.706 to 6.834 mg/g of dry weight obtained during the later vegetative stage. RP-HPLC analysis of the methanolic extract of O. majorana L. dried aerial parts showed the predominance of phenolic acids during the early vegetative stage whereas flavonoids predominate during the other stages of growth. The main phenolic acids identified were trans-2-hydroxycinnamic, rosmarinic, vanillic, chlorogenic, gallic and cinnamic whereas the main flavonoids were amentoflavone, apigenin, quercetin, luteolin, coumarin and rutin. Results obtained showed that later vegetative stage is characterized by the highest contents of bioactive compounds and therefore it could be considered as the best stage for harvesting marjoram plants.     

In vitro propagation and regeneration of an industrial plant kenaf (Hibiscus cannabinus L.)

The present study report a protocol for the efficient in vitro propagation of kenaf (Hibiscus cannabinus L., an industrial crop having high cellulosic fiber content) on hormone free MS medium using the shoot apex and nodal explants. Shoot tips and nodes were isolated from 15 days old seedlings cultivated on MS medium. Different combinations and concentrations of auxin/cytokinin were used and added to the MS medium to assess the shoot and root induction of theses explants. Several subcultures were drived in order to enhance the multiplication rate. Healthy and well developed in vitro propagated shoots were transferred for acclimatization under greenhouse conditions in pots filled with different substrates (sand + compost or perlite). Our results showed that shoots could elongate and root within 4-6 weeks on MS basal medium without any callus formation. However, addition of growth regulators to the MS medium leaded to a decrease in shoot and root induction rates. Indeed, the highest shoot regeneration frequency (90.5%) was obtained on MS control medium. Elongated shoots were transferred onto the same hormone free MS medium using five subcultures where the multiplication rate reached the highest value (3.66) at the fifth and last step. The in vitro rooted plantlets were acclimatized in greenhouse and successfully transplanted to natural conditions with 70% survival.