First Report of Botryosphaeria dothidea Causing Canker and Dieback on Fig Trees in Semi-Arid Orchards

Abstract

Severe canker and dieback symptoms were observed on fig trees cultivated in semi-arid orchard systems, leading to branch decline, bark cracking, vascular discoloration, and gradual reduction in tree productivity. Symptomatic samples collected from infected orchards were subjected to isolation and identification of the associated fungal pathogen using morphological, pathogenicity, and molecular analyses. Fungal isolates consistently produced rapidly growing gray to dark colonies with abundant aerial mycelia and characteristic conidial structures typical of species belonging to the genus Botryosphaeria. Microscopic examination revealed hyaline, aseptate conidia that became pigmented with age, corresponding to morphological descriptions of Botryosphaeria dothidea. Pathogenicity tests conducted on healthy fig seedlings and detached branches reproduced typical canker lesions and shoot dieback symptoms, whereas non-inoculated controls remained symptom-free. Re-isolation of the fungus from artificially infected tissues fulfilled Koch’s postulates and confirmed the pathogenic role of the isolates. Molecular characterization based on amplification and sequencing of the internal transcribed spacer (ITS) region and translation elongation factor 1-α (TEF1-α) gene demonstrated high sequence similarity with authenticated isolates of B. dothidea deposited in public databases. Phylogenetic analysis clustered the obtained isolates within the B. dothidea lineage with strong bootstrap support, confirming species identity and genetic relatedness among isolates recovered from different orchards. Environmental conditions associated with drought stress, high temperature fluctuations, and pruning wounds likely contributed to disease establishment and pathogen spread in semi-arid environments. The occurrence of B. dothidea on fig represents a new disease record and highlights the emerging threat posed by opportunistic canker pathogens in water-limited orchard systems. Accurate identification of the pathogen is essential for early diagnosis and implementation of effective disease management practices aimed at reducing economic losses in fig production.