Effects of the DNA methylation inhibitor, 5-azacitidine on rabbiteye blueberry ‘Tifblue’ fruit ripening

Blueberry (Vaccinium spp.) has been gaining consumer popularity owing to its high anthocyanin contents, which has potential positive effects on human health. As blueberry production continues to increase, the labor-intensive nature of blueberry fruit harvesting has become a major obstacle to efficient production. Each blueberry fruit on a single cluster matures at different times, resulting in high harvesting costs. For efficient blueberry production, blueberry fruit ripening should be artificially manipulated. Blueberry ripening is a complex process involving sugar and anthocyanin accumulations, acidity loss, and berry softening and coloration. Here, the effects of the DNA methylation inhibitor 5-azacitidine (5-AzaC) and fruit ripening-promoting phytohormones abscisic acid (ABA) and ethylene (using the ethylene-releasing reagent ethephon) on rabbiteye blueberry ‘Tifblue’ fruit ripening were determined. Epigenetic regulations are involved in various aspects of fruit ripening; therefore, the effect of 5-AzaC plus ABA and ethylene treatment on blueberry fruit was tested. We conducted injection treatments of 5-AzaC, ABA, ethephon, ABA plus 5-AzaC, and ethephon plus 5-AzaC on large green-stage fruit of field-grown ‘Tifblue’. Independent 5-AzaC (800 μmol L^‑1), ABA (500 mg L^‑1), and ethephon (200 mg L^‑1) treatments promoted berry softening and coloration. Only 5-AzaC significantly increased sugar accumulation, whereas 5-AzaC alone and ABA plus 5-AzaC significantly increased anthocyanin accumulation. When 5-AzaC was applied with ABA, fruit coloration, anthocyanin accumulation, and fruit size were greater than the independent ABA treatment, but the Brix/acidity ratio and sugar accumulation were lower in the combined treatment than in the independent ABA and 5-AzaC treatments. We also found that the 5-AzaC and the ABA plus 5-AzaC treatments increased ethylene production and ABA contents. Although further studies are necessary, these results suggested that 5-AzaC affects the ripening of ‘Tifblue’ fruit at least partially through interactions with ripening-related phytohormone metabolism.