The Effect of Postharvest Methyl Jasmonate Treatment on the Expression of Some Genes of Ethylene Biosynthetic Pathway and Qualitative Properties of Strawberry Fruit

Document Type : Full Paper

Authors

• Saveh Vaezi ¹
• Mohammadreza Asghari ¹
• Alireza Farokhzad ¹
• Nasser Mahna ²
• Morteza Soleimani Aghdam ³

¹ Department of Horticulture, Faculty of Agriculture, Urmia University, Urmia, Iran

² Department of Horticulture, Faculty of Agriculture, Tabriz University, Tabriz, Iran

³ Department of Horticulture, Faculty of Agriculture, Imam Khomeini International University, Qazvin, Iran

Abstract

Keywords

• ACO
• ACS
• Anthocyanins
• Firmness
• Phenolics

Main Subjects

• Fruit Science

Extended Abstract

Introduction

Strawberries are one of the most perishable fruits due to their metabolic activity and sensitivity to fungal rots, especially gray mold rot caused by Botrytis, and are prone to water loss and mechanical damage due to their soft texture and lack of a protective layer. Jasmonates are an important group of non-classical hormones that are naturally produced in a wide range of higher plants and act as signaling agents in many physiological and biochemical processes including ethylene production, defense responses against biotic and abiotic stresses, synthesis of anthocyanins and other phytochemical compounds and product performance. The aim of this research was to investigate the effect of methyl jasmonate on the content of some biochemical compounds and the expression level of some genes involved in the ethylene biosynthetic pathway, as well as its role in reducing fruit decay and increasing the nutritional quality of strawberry, during storage at 3±0.5°C for 10 days.

Materials and methods

Strawberry (Fragaria × ananassa cv. Sabrosa) fruits, were harvested at commercial ripeness time (>75% of the surface red color), from a commercial production greenhouse and transported to the postharvest laboratory of Urmia University. Fruits were selected for uniformity in size and ripening, and lack of defects then treated with different concentration of MeJA (0, 10, and 100 μmol/l), and packed in polyethylene boxes to store for 12 days at 3 ± 0.5 ◦C and 85–95% RH. Fruit quality parameters and ethylene biosynthetic pathway genes expression rates were measured just after harvest (control) and every 4 days until day 12. In order to treat with MeJA vapor, the fruits were transferred 100 × 100 × 4 cm³ boxes containing filter papers impregnated with MeJA (Sigma Aldrich) at room temperature (25 ± 1 ◦C) for 16 h.

Results and Discussion

The results showed that there was no significant difference in the pH of fruit juice during the storage period among treatments. Fruit TSS content was increased during storage, but the increase rate was lower in treated fruits. MeJA significantly maintained fruit TA content. The strawberries treated with MeJA exhibited a significantly higher TA content at the end of the experiment. After 12 days, the ascorbic acid content of strawberries treated with methyl jasmonate 10 and 100 µmol/l was significantly higher than that of the control (P < 0.01). Decay extension symptoms were seen in control fruits on day 8 and reached 2.66% until day 12 during storage. Compared to control, 10 and 100 μmol/l MeJA treatments significantly maintained fruit firmness after 8 and 12 days of storage (P < 0.01).  Total phenolic content in control and MeJA-treated fruits increased during the first 8 days of storage and then declined continuously during the remaining days. The anthocyanin content was increased in fruits treated with MeJA during the first 8 days of storage and then began to decrease. while the control fruits exhibited significantly lower anthocyanin content at the end of storage. Compared with the control, the transcription levels of all evaluated genes including FaACO, and FaACS were significantly higher in fruit received 10 and 100 μmol/l MeJA.

Jasmonates are the main triggers of plant defense systems against biotic and abiotic stresses. Based on the obtained results, methyl jasmonate maintained the pH level and prevented its increase during the storage period. The use of methyl jasmonate in strawberries reduced the increase in the amount of soluble solids compared to control fruits. Methyl jasmonate prevents the reduction of organic acids by delaying the production of ethylene and increasing the activity of antioxidant enzymes after the product ripens. Also, methyl jasmonate treatment, compared to the control, maintained the amount of vitamin C during the storage. The use of methyl jasmonate has reduced the decay rate and increased the marketability of the fruit. The fruits kept their firmness at the end of the storage. The high firmness of fruits treated with methyl-jasmonate may be due to the effect of methyl jasmonate on the enzymes that soften the flesh of the fruit. In this study, methyl jasonate treatment increased total phenol and total anthocyanin in strawberry fruits. Methyl jasmonate causes ethylene synthesis as a growth inhibitory hormone and activates some systems of resistance to biotic and abiotic stresses.

Conclusion

Our results show that the fruits treated with methyl jasmonate have the highest amount of organic acids, vitamin C, total phenol, total anthocyanin, fruit firmness and marketability and the lowest amount of pH, soluble solids and decay compared to the control fruits. Methyl jasmonate facilitates defense processes against biotic and abiotic stresses through the expression of ethylene biosynthetic pathway genes. Therefore, methyl jasmonate can play an effective role in increasing shelf life and maintaining the quality of strawberry fruit.