Anthocyanins contribute to fruit defense against postharvest green mold

Anthocyanins, an important class of pigmented and health-promoting plant secondary metabolites, are involved in protecting plants from stresses. However, the contribution of anthocyanins in plant resistance to biotic stresses is poorly understood compared with that in plant resistance to abiotic stresses. Here, we characterized the function of anthocyanins in protecting fruit from green mold, the major postharvest disease of citrus fruit. Compared with other oranges, 'Tarocco' orange, one of the most important blood oranges enriched in anthocyanins, showed reduced susceptibility to the necrotrophic fungus Penicillium digitatum (Pd) which causes citrus postharvest green mold. Pd infection induced the accumulation of anthocyanins in 'Tarocco' orange and exogenous treatment of anthocyanins significantly reduced the susceptibility of citrus fruit to Pd. The accumulation of reactive oxygen species (ROS), which was shown to contribute to plant infection of necrotrophic fungal pathogens, in 'Tarocco' orange was less than that in other oranges upon Pd infection. ROS content and associated gene expression in citrus fruit upon Pd infection were reduced after exogenous treatment of anthocyanins. Moreover, transcriptome analysis showed that a lot of genes probably participated in plant-pathogen interaction and anthocyanin biosynthesis were noticeably up-regulated in 'Tarocco' orange upon Pd infection. These findings highlight the contribution of anthocyanins to fruit disease resistance and provide significant insights into the control of citrus postharvest green mold.

Automated summary

The study showed that anthocyanins play an important role in plant resistance to fungal pathogens by inducing the expression of genes related to disease resistance and reducing the accumulation of reactive oxygen species associated with fungal infection. This leads to improved resistance of citrus fruit to postharvest green mold, highlighting the potential of anthocyanins in controlling fruit diseases.