Effect of Pre-harvest Application of Putrescine and Post Harvesting Aloe vera Gel on the Quality and Shelf Life of Table Grape (Vitis vinifera cv. ‘Yaghouti’)

Table grapes (Vitis vinifera L.) is one of the most important fruits that is widely grown in the world and is the export fruit of many countries. Although edible grapes are classified as non-climacteric fruits, they are very prone to spoilage due to their softening, weight loss, and decay caused by fungi, as a result which consequently leads to low storability. Different strategies have been postulated to maintain firmness and control decay of table grapes during storage and improve functional properties of fruit such as pre and postharvest chitosan coatin, and exogenous abscisic acid application. Table grapes have a short shelf life due to the thin pericarp and fleshy texture of the fruit. Polyamines (PAs) application also showed a significant role in extending the storage periods of several fruit species with maintenance of fruit quality. Postharvest treatments are not necessarily the best way of maintaining fruit quality during postharvest period. Such treatments are expensive, increase the risk of fruit damage through extra handling and also encourage grower to pay less attention to on-tree quality. Pre-harvest application considered as a good alternative to cope with mentioned problem. To the best of our knowledge, there is not any report in literature about the role of pre-harvest application of Pas and post-harvest table grape in Aloe vera gel (AVG) as a possible role in reducing mechanical damage of berries which leads to lower decays. Besides these, damage caused by human handling starts at harvest operation, which still occurs by hand for most fruits.

This study was done on 12-year-old mature grape varieties of ‘Yaghouti’ in two independent experiments in the scaffolding garden of Abestan region of Khorramabad city and laboratory post harvesting of horticultural sciences department of Lorestan University in 2019. Therefore, this study investigated the effect of foliar application before harvesting of putrescine (PUT) in three different concentrations (0, 2.0 and 3.0 mM) and immersion post-harvest fruit in AVG (25.0 and 33.0%) on grape fruit quality and shelf life of table grape (Vitis vinifera cv. ‘Yaghouti’) in five times (0, 9, 18, 27 and 36 day) during storage at 4° C.  The study was based on a factorial experiment with two pre-harvest spraying factors with PUT and post-harvest immersion in aloe vera gel (AVG) with three replications. The parameters of soluble solids (TSS), titratable acids (TA), ascorbic acid, total anthocyanin content (TCA), total phenol content (TPC), fruit firmness, shelf life of table grape (per day) were measured.

Fruits treated with both PUT concentrations showed greater firmness, vitamin C, total anthocyanin and phenol content, TSS, and during storage retained their shelf life longer than the control. At all five measurements, the highest levels of phenol and total anthocyanin content and firmness were related to the treatment of PUT 2.0 mM with coating of 25% and 33% AVG and the lowest was related to control. Also, pre-harvest use of PUT significantly prevented the softening of the fruit during storage and kept the firmness fruit.  Softening contributes to quality loss in reducing the shelf life, but PAs treatment resulted in maintenance of flesh firmness during cold storage. Therefore, Put- and Spd-treated grape have higher firmness at harvest leading to much lower mechanical injury during harvest and handling process and providing better transportability. The purple skin color of table grape was related to the presence of anthocyanin compounds, from which the anthocyanin malvidin-3-glucoside has been found as major component. Although, total anthocyanins were reduced in control and treated fruits during cold storage, but pre-harvest foliar spraying of Put delayed total anthocyanins concentration after 36 days of storage and decreased the loss of these compounds at the end of experiment. PAs have been described as anti-senescence agents and a great number of researches have been focused on the role of exogenous PAs on fruit ripening. Also it has been reported that the ripening process and senescence of table grapes is correlated with the anthocyanin concentration and profile. However, the data on pre-harvest application of polyamine on different fruit species are scant. Khan et al., (2007) showed that pre storage application of Put would retard fruit softening in ‘Angelino’ plum during cold storage by suppressing ethylene biosynthesis. In mango, Malik and Singh (2005) reported that pre-harvest application of PAs improved fruit shelf life, increased ascorbic acid content and retarded fruit skin color changes compared to control

Pre-harvest foliar application of Put on grapevines maintained higher firmness at harvest and postharvest periods and also improved the fruit quality in terms of phenolics, ascorbic acid, anthocyanin and also controlling weight loss during cold storage. Overall, the results showed that pre-harvest use of 2.0 mM PUT and post-harvest immersion in 25.0% and 33.0% AVG improved the shelf life of the cultivar by 16 days compared to control.