Exogenous Applications of Kaolin and Glycine Betaine Increased the Yield and Quality of Olive Fruit and Olive Oil

This study aimed to determine the effects of kaolin-based particle film technology and glycine betaine, which is one of the osmoprotectants, on the yield and quality of olive fruit and olive oil. During this study, fruiting, and non-fruiting ‘Memecik’ olive trees were treated with 3% and 6% kaolin and 0.3% and 0.6% glycine betaine, in addition to control groups. Kaolin and glycine betaine applications at different doses were sprayed on trees at different intervals (twice or thrice) before flowering, at fruit set, and at the fruit enlargement stage. Accordingly, biochemical, physiological, yield, and quality parameters were analyzed after treatments to determine the effects of glycine betaine and kaolin applications on the yield and quality in olive fruit and olive oil. Among them, some important results were obtained, such as olive oil efficiency, which was greatly increased by both glycine betaine and kaolin, while cooler leaf surface temperature was recorded with kaolin application. Moreover, this study revealed that both kaolin and glycine betaine applications not only increased the production of olive fruit but also oil efficiency was remarkably boosted. Two 0.3% and 0.6% doses of glycine betaine increased the yield of non-fruiting trees up to 25 kg/tree, while kaolin application increased the yield of fruiting trees up to 10 kg/tree. A similar increasing trend in tree yield was observed in fruiting trees. Further, the fatty acid contents of olive oil met the quality standards, and glycine betaine and kaolin induced fruit size. When the results of the trials are considered as a whole, glycine betaine application seems to be at the forefront of the best results in terms of significant criteria. Considering application frequency and dose, two 0.3% doses of glycine betaine was seen to be the most appropriate dose (once before flowering and once after flowering in the fruit set period). The results of this work indicate that yield and quality of olive fruit and oil were improved with both kaolin and glycine betaine applications.