Survey and Pathogenicity of Alternaria alternata Causing Post-Harvest Black Spot on Apple Fruit in Cold Storage

Abstract

Survey and pathogenicity of Alternaria alternata causing post-harvest black spot-on apple fruit in cold storage were investigated to determine disease incidence, distribution, and infection potential under low-temperature storage conditions. Cold storage facilities and apple consignments exhibiting characteristic symptoms such as dark sunken lesions, surface discoloration, and tissue decay were surveyed, and infected fruit samples were collected for pathogen isolation. Fungal identification was conducted based on morphological characteristics including colony pigmentation, conidial shape, and sporulation patterns, supported by molecular confirmation using ITS rDNA sequencing. Results confirmed A. alternata as the predominant causal agent associated with black spot symptoms in stored apple fruit. Pathogenicity tests on healthy apples under simulated storage conditions reproduced typical lesions, confirming the virulence of the isolates at low temperatures. Variation in aggressiveness was observed among isolates, indicating strain-level differences in pathogenic potential. The pathogen demonstrated the ability to persist and infect under cold storage environments, suggesting strong adaptation to post-harvest conditions. Factors such as fruit surface injuries and storage humidity were found to enhance disease development and spread. The study highlights the economic importance of post-harvest losses caused by A. alternata and emphasizes the need for improved storage hygiene and handling practices. These findings support the development of integrated post-harvest disease management strategies to reduce losses in apple supply chains.