Molecular mechanisms involved in the biocontrol of post-harvest pathogen Penicillium digitatum

The predominant disease afflicting citrus fruits is postharvest green mold, which is caused by the fungus Penicillium digitatum ( Pd ). On a global scale, this disease incurs substantial economic losses, particularly in arid and subtropical regions. The absence of advanced storage facilities in underdeveloped and developing nations exacerbates these losses, with damage rates in these regions reaching nearly 30% in developed countries. Currently, synthetic fungicides such as imazalil, thiabendazole, and benomyl are employed to mitigate green mold on citrus fruits. However, applying these fungicides poses environmental hazards, contributes to carcinogenic risks for users, and has increased pathogen resistance. Furthermore, the production of mycotoxins by Pd and the mycotoxin patulin by Penicillium expansum presents significant public health concerns. Consequently, using fungicides is increasingly viewed as inappropriate, prompting researchers to explore alternative strategies that ensure both environmental and consumer safety while establishing sustainable control measures. This includes biological control methods, such as epiphytic and endophytic antagonists, and genome editing techniques, which can manage pathogenic microbes without adverse environmental or human health effects. Ongoing research aims to elucidate the interactions between plants and pathogens, including infection and disease resistance mechanisms. Additionally, it is imperative to investigate the roles of beneficial bacteria and other microbial agents, particularly Bacillus strains and antagonistic bacteria such as Kloeckera apiculata and Bacillus subtilis , in inhibiting green mold. Recent advancements in genome sequencing and improvements in genetic transformation systems have facilitated a deeper understanding of Pd pathogenicity, citrus resistance mechanisms, and interactions between citrus antagonists and Pd . This review synthesizes recent findings on Pd pathogenicity, plant resistance, molecular interactions between pathogens and host plants, and the efficacy of microbial biocontrol agents, as well as the potential impacts of antagonists on Pd infection.