Preharvest Abscisic Acid Application to Alleviate Chilling Injury of Sweet Basil (Ocimum basilicum L.) during Cold Storage

Fresh-cut sweet basil (Ocimum basilicum L.) is highly sensitive to low temperatures during postharvest storage. This study investigates whether preharvest foliar application of different concentrations of abscisic acid (ABA) can increase tolerance of the commercial basil varieties 'Di Genova' and 'Nufar' to chilling injury (CI) during postharvest storage at 3.5 degrees C and at 7 degrees C. Experiments were conducted under greenhouse and commercial open-field conditions in southwest Florida during the 2017/2018 growing season. Our results showed that greenhouse-grown plants were less affected by CI during 9 days of storage at 3.5 degrees C when treated with 1000 mg/L or 1500 mg/L ABA and at 7 degrees C storage compared with the water control, but effects varied by experiment. Preharvest applications of 1000 mg/L ABA were sufficient in reducing CI during cold storage at 3.5 degrees C in basil grown under open-field conditions; however, at 7 degrees C postharvest storage, chilling-induced damage did not differ between ABA and untreated plants. Electrolyte leakage analysis of leaves confirmed the beneficial effects of ABA on alleviating chilling-induced injury. Under greenhouse conditions, preharvest applications of 1000 mg/L ABA were more effective when plants were harvested at 1300 or 1530 HR than at 1100 HR. Our results suggest that 1000 mg/L foliar preharvest applications of ABA in combination with afternoon harvest are an effective strategy to alleviate CI damage during postharvest storage at temperatures less than 4 degrees C and to extend the shelf life of greenhouse or field-grown, fresh-cut basil.