Structure de la communauté fongique associée aux maladies d’oranger (Citrus sinensis L.) cultivé dans la région de Ghardaïa

Abstract

The orange tree (Citrus sinensis L.) is considered one of the most widely grown Citrus fruits in the world. In Algeria particularly, this crop occupies a crucial socio-economic position. However, these trees suffer from significant mortality every year due to various abiotic and biotic factors, such as phytopathogenic fungi. The aim of this study was to study the fungal community associated with orange tree diseases in various orchards in the region of Ghardaïa. Surveys were carried out in two orange groves featuring the cultivars Thomson and Valencia Late, where 20 orange trees showing symptoms of decline were selected, from which 60 twigs were chosen for isolation. The observed lesions in symptomatic branches were categorised into three types namely, central necrosis, sectorial necrosis and black spots. Macro and micromorphological characterization of the 60 fungal isolates obtained enabled us to identify eleven different genera, namely Alternaria, Verticilium, Botrytis cinerea, Gnomoniaceae-like, Cladosporium, Colletotrichum, Sepedonium, Ulocladium, Mucor, Aspergillus and Fusarium, with Alternaria dominating with (52.70%) of the total, followed by Verticilium (16.22%) and Gnomoniaceae-like (10.81%). Pathogenicity tests showed the aggressiveness of Cladosporium sp. Alternaria sp. and Botrytis cinerea, confirming Koch’s postulate. The genera Sepedonium and Gnomoniaceae are reported for the first time in association with Citrus sinensis L., worldwide.