Temperature and light impacts on sunburn, and mitigation by chemical suppressants in ‘Fuyu’ sweet persimmons

Abstract

As global warming intensifies, sunburn damage plagues fruit production. However, research on sunburn occurrence patterns and effective prevention measures for ‘Fuyu’ sweet persimmons has been lacking. This pilot study investigated the impact of strong light and high temperatures on sunburn occurrence in ‘Fuyu’ sweet persimmons, characterized the temporal pattern of sunburn development, and explored the effectiveness of chemical suppressants in mitigating damage. Under weak light conditions, the increase in fruit surface temperatures (FST) compared to air temperature (AT) was minimal, and no sunburn occurred. Conversely, non-acclimated fruits exposed to strong light displayed extensive sunburn damage within a day. Acclimated fruits under strong light revealed differences in sunburn damage observed between treatment groups. The kaolin treatment, which exhibited the lowest browning, also showed a significant FST reduction. The carotenoid content was lower in the kaolin treatment than control. Field trials were conducted to evaluate the effectiveness of sunburn suppressants. Both kaolin and a kaolin-carnauba wax mixture effectively reduced sunburn to 30% of the control. These effective treatments decreased FST by up to 3.5℃, maintained high chlorophyll content, and augmented antioxidant enzyme activities as well as DPPH, ABTS, FRAP, TFC and TPC levels. Notably, the kaolin treatment further enhanced fruit weight, length, width, firmness, and total soluble solids content in hot and high-radiation environments. In conclusion, kaolin treatment combined carnauba wax was identified as the most effective candidate material for preventing sunburn damage in ‘Fuyu’ persimmons under these environmental and experimental conditions. © 2024