Induction of Pigmentation and Anthocyanin Biosynthesis in Harvested Strawberry Fruit by Methyl Jasmonate

Abstract

Strawberry (Fragaria × ananassa) is an important fruit worldwide. The fruit has high nutritional value such as anthocyanins and ascorbic acid. However, strawberry fruit is delicate and highly perishable to mechanical injury, desiccation, and physiological disorders after harvest. Methyl jasmonate (MeJA), a naturally occurring plant endogenous hormone, plays an important role in plant development, fruit ripening, and defense mechanism. Furthermore, postharvest application of MeJA has been reported to effectively enhance antioxidant capacity in berry fruits including strawberry and suppress postharvest diseases caused by necrotrophic pathogens. In this study, the effects of postharvest MeJA treatment on anthocyanin biosynthesis and postharvest decay in Seolhyang strawberry fruit were investigated. Peduncles of strawberry fruits were immersed in 100 μM MeJA solution and stored at 10 ± 0.5oC and 90 ± 5% relative humidity for 3 weeks. Fruits firmness and respiration rate were not significantly affected by MeJA. Red coloration by MeJA was significantly increased to a greater degree compared to that in control. Total anthocyanins contents were higher in MeJA treatment (27.5 ± mg·100g-1 fresh weight) than in control (13.4 ± mg·100g-1 fresh weight) at 2 weeks in storage. Changes in phenylalanin ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and flavonoid 3-O-glucosyltransferase (UFGT) mRNA levels involved in anthocyanin biosynthesis were measured by quantitative reverse transcription polymerase chain reaction (RT-qPCR). PAL and CHS expression levels were higher than CHI, F3H, DFR, ANS, and UFGT expression levels in control fruits at 3 and 6 days in storage. CHI, F3H, DFR, ANS, and UFGT expression levels in MeJA treatment were higher than those in control fruit at 6 and 8 days in storage. On the other hand, the expression level of genes involved in anthocyanin biosynthesis were higher in control fruits than in MeJA treated fruits after 10 days in storage. These results suggest that postharvest MeJA treatment on Seolhyang strawberry fruits increased the red coloration by up-regulating mRNA expression of these genes during early storage. The MeJA treatment significantly reduced fruit decay. At the end of storage, decay rate in MeJA treatment was only 21%, whereas 67% of fruit decay was shown in control fruit. Exogenous MeJA treatment also increased endogenous MeJA contents in the strawberry fruits. These results indicated that MeJA can effectively improve red coloration by increasing anthocyanin biosynthesis and reduce decay on Seolhyang strawberry fruits. Thus it will help to elucidate the ripening mechanism of non-climacteric strawberry fruit, and it will be beneficial in distributing the high quality strawberry through developing the decay inhibition technique by MeJA.