Pre‐harvest methyl jasmonate treatments increase antioxidant systems in lemon fruit without affecting yield or other fruit quality parameters

Abstract

BACKGROUND Jasmonic acid (JA) and its volatile derivative methyl jasmonate (MeJA) are hormones involved in the regulation of many processes in plants and act (when applied as a post‐ or pre‐harvest treatment) to increase fruit bioactive compounds with antioxidant potential. However, there is no literature available regarding the effect of pre‐harvest MeJA treatment on lemon fruit antioxidant systems, which was the aim of the present study. RESULTS MeJA treatment (0.1, 0.5 and 1.0 mmol L–1) increased antioxidant compounds, such as phenolics, in the juice and flavedo of ‘Fino’ and ‘Verna’ lemons at harvest, with the most effective concentration being 0.1 mmol L–1 in both cultivars. In addition, catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) activities were also increased by MeJA treatment, with the highest increases being also found with 0.1 mmol L–1. The increases in APX and CAT were maintained from one treatment to another during fruit development on the tree, whereas the increase on POD disappeared after 8–10 days of each treatment. For both antioxidant systems, the highest increases were found in lemon harvested at the commercial ripening stage. By contrast, crop yield, fruit ripening process and quality parameters were generally not affected by MeJA treatment. CONCLUSION Preharvest MeJA treatment could be a useful tool for increasing antioxidant potential and the health beneficial effects of lemon fruit consumption, given the relationship between these properties and phenolic content. Moreover, the increased concentration of phenolics and the activity of antioxidant enzymes in the flavedo of MeJA treated fruit could increase lemon tolerance to chilling injury and decay during postharvest storage. © 2019 Society of Chemical Industry

Preharvest application of methyl jasmonate increases crop yield, fruit quality and bioactive compounds in pomegranate ‘Mollar de Elche’ at harvest and during postharvest storage

“…Thus, preharvest treatments of plum trees with several concentrations of MeJA (0.5, 1, and 2 mmol L ‐1 ) increased crop yield, fruit size and weight in ‘Black Splendor’ and ‘Royal Rosa’ cultivars, the most effective concentration being dependent on cultivar while no effect was observed on number of fruit per tree . In a similar way, 0.01 and 0.1 mmol L ‐1 preharvest MeJA treatments increased berry size and total yield in ‘Magenta’ and ‘Crimson’ table grape cultivars, while MeJA application to lemon trees, from 0.1 to 1.0 mmol L ‐1 did not affect yield or fruit weight . In the present experiments, the increase in yield was due to an increase in the number of harvested fruits showing that MeJA applied at these concentrations could have reduced the abscission process during fruit growth and ripening on tree together with an increment in the plant photoassimilates available to support fruit growth.…”

“…Currently, most of the knowledge about MeJA effects on fruit quality attributes and ripening is derived from postharvest treatments, which have been focused on reducing a number of stress‐induced injuries during the postharvest period such as chilling injury, infection by some pathogens and mechanical stress among others . In addition, MeJA treatments applied as foliar spray during fruit development on tree, either in climacteric or non‐climacteric fruits, have been reported to increase phenolic and anthocyanin concentrations in table grapes, plums, black currants and apples as well as phenolic concentration in juice and flavedo of lemon fruits . Similar effects of preharvest MeJA treatments on increasing phenolic compound have been achieved on artichoke heads .…”

“…). Accordingly, MeJA treatments led to accumulation of anthocyanins and other polyphenol compounds in plums, black currants, mangos, apples, table grape, grapevine and wines and artichoke heads as well as in juice and flavedo of lemon fruits, as a result of enhanced phenylalanine ammonialyase (PAL) activity and increased expression of genes codifying enzymes involved in anthocyanin biosynthesis pathway . Then, MeJA treatments would lead to improved quality and health properties of pomegranate consumption, given the role of phenolics, including anthocyanins, and ascorbic acid in these properties …”

“…Control trees were sprayed with distilled water containing 1 mL L −1 Tween‐20. The concentrations and dates of application were selected based on previous experiments with other fruits such as table grape, plum and lemon and taking into account the harvest dates of this cultivar in similar growing conditions in previous seasons, so that the first treatment was applied before the skin and colour changes and the last one 4 days before the first harvest. Pruning, thinning, fertilization [nitrogen/phosphorus/potassium (N/P/K) 160/80/160] and irrigation by using 4 L per hour‐water pipes (April: two watering cycles of 1 h per week, May, June, July, August and September: two watering cycles of 2 h per week and October: one watering of 1 h) were carried out during the experiments according to standard cultural practices for pomegranate.…”

Thymol Encapsulated into HP-β-Cyclodextrin as an Alternative to Synthetic Fungicides to Induce Lemon Resistance against Sour Rot Decay

“…However, in fruit treated with 25 and 50 mM of HP-β-CD-thymol or propiconazole, these antioxidant enzyme activities increased during storage; the highest values were observed with 50 mM HP-β-CD-thymol treatment for the three enzymes ( Figure 5 ). Decreases in the activity of antioxidant enzymes (CAT, POD and APX) during on-tree lemon fruit development were reported by Serna-Escolano et al [ 39 ]. However, the increased antioxidant enzyme activities found in treated lemons agrees with previous reports, in which treatments of mango [ 40 ] and avocados [ 38 ] with thymol or thyme essential oils improved antioxidant enzyme activities and free radical scavenging activity and enhanced resistance of fruit tissues against fungal decay.…”