Diversité et pathogénicité du mycobiote associé à l'olivier (Olea europaea L.) cultivé dans la région de Ghardaïa

Abstract

The olive tree (Olea europaea L.) is one of the most widespread fruit trees in the Mediterranean countries where it plays a very important socio-economic role. However, this tree counts considerable mortalities each year because of several biotic and abiotic factors, including fungal pathogens. This study focuses on the diversity and pathogenicity of mycobiota associated with olive trees in different orchards in the region of Ghardaïa. The prospecting were carried out in three olive groves include the varieties Chemlal and Sigoise. In field, 15 symptomatic olive trees were chosen and 45 branches were taken to make the isolations. The necrosis observed in symptomatic branches were classified into three types namely, sectoral necrosis, central necrosis and black spots. The macro and microscopic characterization of the 58 fungal isolates obtained, allowed us to identify eight different genera, namely, Aspergillus, Cladosporium, Sepedonium, Alternaria, Cylindrocladium-like, Colletotrichum, Verticillium and Gnomoniaceae-like, with the latter’s dominance with 70,69% of the total, followed by Colletotrichum (10,34%), Aspergillus (5,17%) and Cladosporium (5,17%). Pathogenicity tests showed the aggressiveness of Aspergillus sp., Cladosporium sp. and Sepedonium sp., with the confirmation of Koch’s postulate. The genera Sepedonium and Cylindrocladium are reported by the first time in association with Olea europaea L. in the world. Thus, Colletotrichum is found for the first time in Algeria.