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.
