Effect of kaolin on tree physiology, superficial sunburn and fruit quantitative and qualitative characteristics of two commercial apple cultivars

This study was carried out to examine the effects of kaolin spray for reducing the adverse effects of high radiation and temperature, especially on fruit sunburn in apple. Treatments were four concentration of kaolin (0, 2, 4, and 6%) and two important and commercial apple cultivars in Fars province; ‘Golden Delicious’ and ‘Starking Delicious’. Trees physiological parameters, fruit sunburn and fruit quantitative and qualitative characteristics were measured. Results showed that as kaolin concentration increase, net photosynthesis was increased and leaf temperature and transpiration were decreased in both cultivars. Incensement of kaolin concentration lead to reduced sunburn symptoms in both cultivars but ‘Starking Delicious’ showed more sunburn than ‘Golden Delicious. Kaolin treatments (with no differences among them) improved almost all of fruit quantitative parameters in comparison to control. Among fruit qualitative characteristics, kaolin treatments increased dry mater and background color and reduced russeting and water core incidence. Kaolin spray didn’t have any significant effect on fruit firmness, total soluble solids, acidity and surface color. Regarding mentioned results, it could be concluded that kaolin spray can be a useful approach to reduce adverse effects of high irradiation and temperature in apple orchards.