2017 ASHS Annual Conference

Sunburn is a physiological disorder associated with excessive sunlight and can severely affect pomegranate fruit quality. Anecdotal observations show that ‘Apseronski’, ‘Kazake’, ‘Kunduzski’, ‘Russian 8’, ‘Salavatski’, and ‘Surh Anor’ pomegranate experienced severe fruit sunburn in El Paso environmental condition. An on-farm trial was conducted in Marcelino Nursery (Tornillo, TX) to evaluate the effects of 30% shade cloth and 60 g·L^-1 aqueous suspension of Surround^® WP (95% kaolin clay) on pomegranate fruit sunburn. Pomegranate plants of the above six cultivars were selected and labeled into three groups: full sun, 30% shade, and kaolin clay. On 2 June 2016, DeWitt woven polypropylene shade cloth was installed above the canopy of the selected pomegranate plants, while kaolin clay was sprayed to completely cover all fruits of the selected plants. On 9 June, kaolin clay was sprayed again. In middle October, all fruits were harvested, and each fruit was visually rated into four groups depending on the area of the fruit surface with sunburn [0: without any sunburn; 1: <10% of fruit surface area affected by sunburn (minimum), 2: 10-50% of the fruit surface area affected by sunburn (mild), 3: >50% of the fruit surface area affected by sunburn (severe)]. Fruit fresh weight, size, and brix value were also measured. The percentage of fruits without any sunburn (group 0) was higher in 30% shade cloth than in kaolin clay and full sun. In group 1, no significance was observed among treatments. In group 2, 30% shade cloth decreased the fruit sunburn of ‘Apseronski’ and ‘Russian 8’ plants and tended to decrease the fruit sunburn of the remaining cultivars. In group 3, ‘Russian 8’ and ‘Salavatski’ plants in 30% shade cloth had reduced fruit sunburn compared to those in full sun and kaolin clay. All fruits had similar fresh weight, fruit size, and brix values. In conclusion, 30% shade cloth could reduce the fruit sunburn of ‘Apseronski’, ‘Kazake’, ‘Kunduzski’, ‘Russian 8’, ‘Salavatski’, ‘Surh Anor’ pomegranate without changes in their fruit quality as indicated by fruit size and brix value. More studies are needed to quantify the effects of kaolin clay on pomegranate fruit sunburn.