Occurence of impietratura and stubbom diseases in grapefruit variates in eastern mediterranean region

59 SUMMARY In this study, grapefruit orchards located in the Eastern Mediterrenean region of Türkiye were surveyed for the occurrence and incidence of stubborn disease and impietratura. Citrus stubborn disease, caused by Spiroplasma citri, was diagnosed in October and November the most suitable time for development of symptoms and collection of plant material. According to symptoms, 37% of the grapefruit trees were indexed as "healthy", 22% as "infected", and 41% did not show clear symptoms, thus they were attributed as "suspected". While it was difficult to observe any clear symptoms in trees elder than 20 years, this was considerable easy for younger trees being 5-15 years old. Trees elder than 20 years were almost all white Marsh seedless, whereas the younger trees consisted mostly of pigmented varieties. Common field symptoms were spooned-shaped and upright growing leaves, shortened intemodes as well as off-season flowering. Trees were slightly too serious stunted. On infected trees fruits of all maturity status were found at the same time, being often smaller, lop-sided, and deformed. Other symptoms, known to occur in stubborn infected sweet oranges, like aborted seeds, acorn-shaped fruits and Zn-defiency were not observed on grapefruit. From each group (healthy, infected, suspected), five randomly selected grapefruit trees were chosen and further diagnosed by biological indexing, culture assay, and ELISA. The trees from the "infected" group were indexed positively for S. citri by biological indexing and culture assay, but the pathogen was not60 detected by ELISA. All grapefruit trees classified as "healthy" or "suspected" were prove to be free of S. citri according to the results of biological indexing, cultere assay, and ELISA. Impietratura was diagnosed by field symptoms like gum showing in the albedo and apparance of many small fruit, which harden, drop to the ground Marsh seedless trees were frequently infected by impietratura; about 23% of all trees examined were infected. The infection rate was considerable low on pigmented varieties estimated as 1,88 % for Red blush, and 0,39 % Star ruby. The impietratura infection of selected grapefruit trees, showing symptoms in field by biological indexing. However, results are forthcomming.