Screening the response of Greek olive cultivars to Xylella fastidiosa infections

In this work we evaluated the response of the major Greek olive cultivars, locals from Crete and North Aegean islands, to the infections caused by Xylella fastidiosa subsp. pauca (Xfp). Isolates of this subspecies have been found to severely impact olives, with severe desiccations on the canopies leading to tree decline in highly susceptible cultivars. Huge research efforts are devoted to screen the response to the infections of a large number of cultivars representing the vast Mediterranean olive germplasm. In the framework of the projects CERTIFIED NURSERIESa and XYLEVAb a collaboration was established between the Greek and Italian research centers to assess the vulnerability of Greek cvs to Xfp. Briefly, plants of the cultivar Adramitini, Kolovi, Throubolia N. Aegean, Amfissis, Chalkidikis, Gaidourelia, Throuba Kritis, Throuba Thassou and Tsounati, are currently under testing. For the first three cultivars, phenotypic assessment and diagnostic tests have been completed at 2 years post-inoculation, while they are still ongoing for the remaining cultivars. For these three cultivars systemic infections were detected in 80-100% of the replicates, similar to that of the susceptible control, the cultivar Ogliarola salentina, which also showed defoliation, shoot dieback and complete desiccation of the plants. Although, none of the infected plants of the three N. Aegean cultivars showed severe symptoms as those reported in the control, defoliation and shoot dieback were recorded, with slightly higher impact on Throubolia N. Aegean. It should be remarked that in the cv Adramitini a slower rate of plant colonization and symptoms progression were recorded. Assessments are ongoing for the remaining cultivars.