Pathogenicity and Cultural Variability of Alternaria citri Causing Black Rot on Citrus Fruit in Post-Harvest Conditions

Abstract

Black rot caused by Alternaria citri is an important post-harvest disease of citrus fruits that leads to significant economic losses during storage, transportation, and marketing. The pathogen infects fruits through wounds or natural openings, resulting in dark necrotic lesions, internal tissue decay, reduced fruit quality, and shortened shelf life. Understanding the pathogenicity and cultural variability of A. citri is essential for improving disease diagnosis and developing effective post-harvest management strategies. The present study was conducted to evaluate the pathogenicity and cultural characteristics of Alternaria citri isolates associated with black rot disease of citrus fruits under post-harvest conditions. Infected citrus fruits exhibiting typical black rot symptoms were collected from storage facilities and local markets, and fungal isolates were obtained using standard isolation methods. Morphological and cultural variability among isolates were assessed based on colony color, texture, growth pattern, sporulation, and pigmentation on different culture media. Pathogenicity tests were performed by inoculating healthy citrus fruits with representative isolates under controlled storage conditions to confirm disease development and compare virulence levels. The results confirmed the association of A. citri with black rot symptoms in citrus fruits. Considerable variation was observed among isolates in colony morphology, growth rate, and sporulation characteristics, indicating substantial cultural diversity within the pathogen population. Pathogenicity assays demonstrated differences in virulence among isolates, with highly aggressive strains causing rapid lesion expansion and extensive fruit decay. Environmental conditions such as high humidity and warm storage temperatures were found to favor disease progression and pathogen growth. The study highlights the importance of understanding cultural and pathogenic variability in A. citri populations for effective disease management. The findings provide valuable insights into the biology and post-harvest behavior of the pathogen and support the development of integrated storage and handling practices aimed at reducing citrus fruit losses during post-harvest processing and distribution.