عنوان مقاله [English]
The present research was conducted to investigate the efficacy of preharvest NaHS application as foliar spraying on the quality and antioxidant capacity of kiwifruits cv. Hayward during cold storage.
In the present investigation, the effects of a preharvest treatment with H2S donor NaHS in four levels (0, 0.5, 1 and 1.5 mM) at 110, 125, and 140 days after full bloom on nutritional quality and antioxidant capacity of kiwifruit (Actinidia deliciosa 'Hayward') were evaluated during 90 days of storage at 1 °C and 90% relative humidity. Sampling was done to measure the desired traits during four periods of 0, 30, 60 and 90 days after storage.
The results showed that NaHS treatment had a significant effect on the evaluated traits. At the end of 90 days of storage, NaHS treatment prevented fruit weight loss and maintained fruit firmness in comparison to the control. The percentage of electrolyte leakage and the amount of accumulated malondialdehyde (MAD) in all concentrations of NaHS was lower in comparison to the control. Preserving ascorbic acid content and increasing the activity of phenylalanine ammonialyase (PAL) lead to higher production of total phenol and flavonoids and improve the antioxidant capacity of fruits. NaHS treatment decreased the activity of polyphenol oxidase in comparison to the control.
NaHS at 1.5 mM showed the best effect among the applied treatments. According to the obtained results, this concentration can be recommended as a suitable treatment to maintain the quality of kiwifruit cv. Hayward.
Using of natural and organic compounds without harmful environmental effects in the production of horticultural products is considered as a new idea in reducing waste before and after harvesting, as well as increasing the storage life of horticultural products and maintaining antioxidant activity in developed agriculture. Pre-harvest application of nutrient solutions, such as H2S donor NaHS, increases the quality and quantity of crop and enhances its storage life and marketability. H2S is currently considered as the third gas signal after nitric oxide and carbon monoxide. Hydrogen sulfide is used as a signaling molecule to reduce chilling injury, delay senescence, and maintain the quality of horticultural products during cold storage. Hydrogen sulfide is produced through enzymatic reactions in many plant species and plays diverse roles in different physiological processes. In addition, this substance acts as an antioxidant molecule to deal with abiotic stresses by reducing the biosynthesis of ROS and increasing the activity of antioxidant enzymes. The H2S donor NaHS treatment has been reported to alleviate chilling injury of hawthorn fruit during cold storage by promoting H2S accumulation via triggering L-cysteine desulfhydrase and D-cysteine desulfhydrase enzymes activity. Treated fruit also showed higher DPPH scavenging capacity by enhancing phenolic compounds accumulation and antioxidant enzyme activity (Aghdam et al., 2018). Luo et al. (2015) reported that the attenuating banana fruits chilling injury by exogenous NaHS (0.5 mM) applying may be attributed to higher endogenous proline accumulation arising from higher pyrroline-5-carboxylate synthetase activity and lower proline dehydrogenase activity accompanied by greater accumulation of phenolic compounds arising from higher PAL activity. Moreover, malondialdehyde, H2O2 and superoxide anion accumulation were reduced by H2S treatment with up-regulated ROS scavenging enzyme activities including catalase, guaiacol peroxidase, superoxide dismutase, ascorbate peroxidase and glutathione reductase, which are beneficial for keeping membrane integrity (Luo et al., 2015).
Material and Methods
The experiment was carried out on 10-year-old kiwifruit vines, in a commercial orchard, located in Gilan Province. Vines were selected with uniform size in terms of growth, yield and fruit load, then sprayed with NaHS at four levels of 0, 0.5, 1 and 1.5 mM. and control vines received only distilled water. Foliar spraying was performed in three stages, (110, 125 and 140 days after full bloom stage) and Tween 20 was used as a surfactant. This experiment was designed based on a factorial and a randomized complete block design with three replications. The fruits were harvested in November with soluble solids content (TSS) of 6.5-6.2% and then transferred to the post-harvest physiology laboratory of the University of Zanjan. The treated fruits were stored for 90 days at 1 ° C with 90% RH. Sampling was done at harvest time and after 30, 60 and 90 days of storage and some quantity and quality traits such as weight loss, tissue firmness, TSS, total acid (TA), ascorbic acid, electrolyte leakage (EL), malondialdehyde (MAD), total phenol and flavonoids, antioxidant capacity, and also the activity of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) enzymes were evaluated.
Results and Discussion
The ANOVA results showed that NaHS, storage time, and interaction of NaHS and storage time had a significant effect (p≤0.01) on evaluated traits. All treatments maintained the antioxidant capacity, total phenol and flavonoids content and PAL activity at a higher level compared with control. The amount of fruit tissue firmness, TA and ascorbic acid decreased by increasing the storage time, and at the third month of storage, the lowest amount was observed in the control fruit. Also, comparing the interaction of the mean of treatments and storage time showed that weight loss, TA, TSS, antioxidant capacity, total phenol, flavonoids and PAL enzyme activity increased during storage time. At the end of the storage time, the highest level of TSS, weight loss, PPO enzyme activity were observed in the control fruit. The lowest antioxidant capacity (52.63 %) was observed in the control treatment at harvest time and the highest in 1.5 mM of NaHS treatment at the end of storage period. Comparing the means showed that at the first 30 days of storage, the highest PAL enzyme activity occurred in the treatment of 1.5 mM of NaHS. Treatment of 1.5 mM NaHS had higher PAL activity. The direct and positive relationship of this enzyme with the synthesis of phenols and flavonoids has been discovered in the fruits of blood orange, strawberry and blueberry. The results of the comparison of the means showed that the total phenol and flavonoids increased during storage time. The lowest total phenol (23 mg GAE.100 g-1 FW) was observed in control fruit at harvest time and the highest (57.99 mg GAE.100 g-1 FW) content of total phenol occurred in 1.5 mM of NaHS at the third month of storage. Plants release phenolic compounds in response to some messenger compounds that play an important defense role. Studies showed that there is a positive relationship between total phenol content and their antioxidant activity. Also, the concentration of 1.5 mM NaHS maintained high levels of vitamin C and firmness of fruit tissues, slowed down fruit weight loss, and decreased ion leakage and accumulation of malondialdehyde and hydrogen peroxide compared to other treatments.
NaHS at 1.5 mM showed the best effect among the applied treatments and according to the obtained results, this concentration can be recommended as a suitable treatment to maintain the quality of kiwifruit cv. Hayward.