No abstract

Many plant species produce phenolic compounds in their various organs and their use in crop protection. These plant secondary metabolites may serve as toxins against the insect pests. The objective of this study was to evaluate in vitro the bio-insecticidal effect of an aqueous extract of wild Olive leaves on Psylla larvae (Euphyllura olivina), a primary pest of the cultivated Olive tree (Olea europaea L. subsp sativa). Two concentrations of 0.05g/ml and 0.1g/ml leaves grinding powder in distilled water were sprayed on branches infested with Psylla larvae. The obtained results revealed a very significant mortality rate of the larvae 24 hours after spraying. The chemical composition of Oleaster leaves aqueous extracts is determined by HPLC-DAD. The results show in majority the presence of phenolic compounds represented by oleuropein and its metabolite hydroxytyrosol. The phenolic compounds of the crude extract were at the origin of this mortality. The Analysis of Variance revealed highly significant results both between the sampled trees and between the tested concentrations. The Principal Component Analysis (PCA) revealed a close relation between the physiological state of the studied trees and the degree of their infestation by the phytophagus. Taking into account, the physical and chemical characteristics of the sampled soils, data analysis showed that trees growing on nitrogen-rich soils were more infested than those growing on soils rich in organic carbon (Corg) and phosphorus (Porg).

Because of the global warming threat, multidisciplinary studies of arid environment ecology are highly expected. In four populations of Atlas pistachio (Pistacia atlantica Desf.) located in Algeria along an aridity gradient, both the taxonomic diversity and the morphological types of communities of arbuscular mycorrhizal fungi (AMF) in rhizospheric soil were assessed. AMF taxonomic richness was low in all sampled populations, with a dominance of the Glomeraceae family. The AMF morphological Arum type was identified in fine roots of all sampled individuals, and the Paris type only in those sampled in the two less arid sites. Along the increasing aridity gradient, climatic conditions would be a determining factor in the decrease of the AMF taxonomic richness within Atlas pistachio rhizospheric soils; it could also indirectly influence the expression of both morphological types (Arum and/or Paris) within Atlas pistachio fine roots.

Medicinal plants are an inexhaustible source of molecules. They are colonized by mycoendophytes, fungi living in their tissues without apparent symptoms. These fungi can provide secondary metabolites with biological activities. It is with this in mind that we are interested in a spontaneous plant from the dayas region (Laghouat, Algeria): Peganum harmala or Harmel, a toxic medicinal plant belonging to the family Zygophyllaceae. Our study consists in highlighting the antibacterial activity of four kinds of mycoendophytes: Cladosporium, Alternaria, Aspergillus and Penicillium isolated from the leaves of this plant. The antibacterial activity is evaluated by the technique of the double disk diffusion on agar with respect to some Gram-positive bacterial strains. We have adopted two protocols for this purpose. For the first, the mycelia of all the mushrooms are deposited in the same petri dish. For the second, a single disc of the mycelium of a single species is deposited per box. The results obtained show a difference in the sensitivity of the bacterial strains to the bioactive substances of the mycoendophytes studied. The Alternaria genus showed the most significant activity. ANOVA performed between the mean diameters of the mycoendophyte inhibition zones and the antibiotic test disc: Chloramphenicol showed a highly significant difference between these two measurements. The Newman-Keuls test revealed a difference in the susceptibility of bacterial strains to the secondary metabolites of fungus mycoendophytes of Peganum harmala according to the two protocols used. The antibacterial effect is related to interactions between endophytic fungi and their host plant.