In this experiment, we tested the exogenous melatonin (0, 1, 10, 100, and 1000 μM) injection at the light green stage for the regulation of strawberry (Fragaria annanaca cv. Sabrina) fruit ripening. Our results showed that a higher endogenous content of melatonin resulting from higher expressions of TDC, SNAT, T5H, and ASMT in response to 1000 μM melatonin injection may be attributed to an accumulation of H2O2 resulting from a higher expression of NADPH oxidase. Also, a higher endogenous accumulation of ABA (due to a higher expression of NCEDs genes) and a higher accumulation of anthocyanin (due to higher expressions of PAL and CHS genes) may be attributed to a higher expression of the GAMYB gene and a lower expression of SnRK2.6 gene, resulting from the endogenous accumulation of melatonin, involved in the ripening of strawberry fruits. Therefore, our results indicate that the exogenous application of melatonin can accelerate the ripening of strawberry fruits by 2–3 days.
