Growth, physiological and biochemical response of six commercial olive cultivars to kaolin foliar application in warm conditions

In order to investigate the effects of kaolin foliar application on growth, physiological and biochemical characteristics of some olive cultivars in Dalahu Olive Research Station in Sarpolzahab city, a factorial experiment in a randomized complete block design with three replications and two factors (cultivars) Olive and kaolin concentrations) was done in year 2020. The planting distance was 6.6 m. Experimental materials of this study were 15-year-old trees of six olive cultivars including Amphisis, Seville, Roughani, Manzanillo, Konservolia and Zard. Two stages of complete foliar application of olive trees with kaolin at zero concentrations as control (foliar application with water) and 2 and 4%, in mid-July and August (due to warm and dry weather during this period), And its effects on growth, physiological and biochemical characteristics of olive cultivars were evaluated. Tree care and maintenance operations were applied equally in all treatments. vegetative traits such as growth and diameter of the current-season shoot growth and current-season shoot diameter as well as relative leaf water content, ion leakage, leaf proline content, total soluble sugars and chlorophyll content  and catalase and peroxidase activity were recorded in different treatments and different cultivars.The results showed that the response of olive cultivars to foliar application of different levels of kaolin was different. Foliar application of kaolin improved growth traits, relative leaf water and chlorophyll content of olive cultivars under warm conditions. Also, kaolin used in olive cultivars reduced the accumulation of malondialdehyde, which was associated with increased activity of antioxidant enzymes. In general, the results of this study showed that kaolin spraying can be used to protect olive tree in warm regions.