Evaluation of the aggressiveness and sporulation of the citrus green mold pathogen,Penicillium digitatum, in Northern Iran

Green mold, caused by Penicillium digitatum, is the most destructive postharvest disease in citrus, leading to major economic losses globally. This study aimed to assess the epidemiological traits, pathogenicity, and aggressiveness of P. digitatum isolates from citrus fruits in Northern Iran. A total of 150 citrus samples were collected from orchards and warehouses across three regions. Isolates were purified using the single-spore method and examined microscopically. Pathogenicity tests involved inoculating oranges with spore suspensions, recording infection frequency (IF), lesion area (LA), sporulation capacity (SC), incubation period (IP), and latent period (LP). Data analysis included ANOVA, Pearson correlation, regression, and cluster analysis. All 88 isolates showed 100 % pathogenicity. LA ranged from 40-80 %, and SC from 7.25×107 to 2.37×108 spores. The average IP and LP were 2.3 and 5.4 days, respectively. A strong correlation (r = 0.8) was found between SC and the composite aggressiveness index (CAI), while IP and LP were inversely correlated with CAI. Cluster analysis grouped isolates into four categories based on aggressiveness, indicating genetic diversity without geographic clustering. These findings demonstrate the high aggressiveness of P. digitatum isolates in Northern Iran and underline the urgent need for targeted postharvest management strategies. This research contributes to understanding the pathogen’s behavior and supports future development of region-specific control measures.