ROOT ROT DISEASES INFECTING OLIVE ORCHARDS IN EGYPT

Abstract

Root rot disease was studied in several olive nurseries and orchards in Ismailia, Behera, Giza and Fayoum governorates. Observed disease symptoms were leaves internal rolling, partial wilt, yellowing or browning of leaves, drying of branches and leaves, twig dieback and severe root rot.Fusarium konzum was the most pathogenic fungus, followed by F. solani. All evaluated olive cultivars were susceptible to infection by the tested fungi however, cultiver Picual was the most susceptible while Koratina was the less one. The infection of Picual, Maraki, Kroneiki and Koratina with F. konzum increased the amount of total sugars while decreased total sugar contents and non-reducing sugars in Toffahi. Also, the infection of olive transplants of cultivar Kroneiki with F. konzum or F. solani increased the total phenols however, decreased the total phenols in cvs. Toffahi, Maraki and Koratina. Oleuropin, Pyrogallol and E-vanillic increased in infected olive transplants of cv. Picual with F. konzum or F. solan. The highest amount of flavonoids was found in tissues of cvs. Koratina and Picual. The oxidative enzymes peroxidase, polyphenoloxidase and catalase recorded an increment in infected tissues of the tested olive cultivars compared to the control and catalase was the highest activity however, polyphenoloxidase was the least one. Transmission electro