Methyl jasmonate and salicylic acid treatment changes the nutritional quality, antioxidant profile and gene expression of postharvest blackberry fruit

Blackberry fruit is rich in various nutrients and has strong antioxidant activity. However, these fruit are soft, juicy, prone to decay and spoilage, and not suitable for storage. To ensure the quality of blackberry fruit and extend its shelf life, this study used methyl jasmonate (MJ), salicylic acid (SA), or MJ+SA to treat mature blackberry fruit after harvesting. And measure the fruit appearance indicators, antioxidant contents, antioxidant enzyme activities, and related gene expression levels stored at 4 °C for different durations. The results showed that the MJ, SA, and the combination of MJ+SA treatments could slow fruit softening by increasing antioxidant contents and antioxidant enzyme activities, with MJ+SA having the greatest effect on the postharvest treatment of blackberry. Compared with those in the control, the DPPH radical scavenging capacity, total phenol and flavonoid contents, and antioxidant enzyme (POD, GSH, and SOD) activities were increased in three hormone treatment groups. Moreover, the expression levels of key genes involved in flavonoid and phenol compound synthesis were upregulated in all the postharvest treatment groups. There was a positive correlation between the contents of total phenol and flavonoid and between their related structural enzyme-encoding genes and transcription factors. This study lays the foundation for further exploration of hormone application for prolonging the shelf life and changing in the antioxidant activity of blackberry fruit.