Postharvest quality maintenance of 'Crimson Seedless' grapes by preharvest applications

The present study was carried out during both 2018 and 2019 growing seasons on ‘Crimson Seedless’ grape vine grown on sandy soil. Vines received water, salicylic acid 200 mg/L, chitosan 10 g/L, putrescine 5 mM, phenylalanine 400 mg/L, ascorbic acid 500 mg/L, citric acid 700 mg/L, gibberellic acid 20 mg/L, active dry yeast 15 g/L at véraison (change of color) stages and at 10 days before harvesting time. Fruit clusters were harvested when total soluble solids (TSS) reached 16%, stored at 0°C and 85–90 relative humidity for 35 days then kept 2 days at shelf life (25 ±2°C and air humidity 70 ±2). Results at harvest time showed that, salicylic acid, putrescine, gibberellic acid and yeast increased average berry weight and juice volume. Salicylic acid, chitosan, putrescine, citric acid and gibberellic acid maintained the berry adherence strength and firmness. Salicylic acid, chitosan, putrescine and phenylalanine increased berry red color, as well as berry anthocyanin, TSS and sugars content. Highest acidity content was obtained by salicylic acid, chitosan, citric acid and gibberellic acid spraying. Results after cold storage and shelf life showed that, berry weight loss decreased significantly by all chemical sprays, except phenylalanine. High maintenance of berry adherence strength and firmness occurred by gibberellic acid followed by putrescine. All chemicals reduced the unmarketable grapes except the phenylalanine.