Characterization and Pathogenicity of Pythium -Like Species Associated with Root and Collar Rot of Kiwifruit in Turkey

During the period of June to October in 2018, a widespread decline was observed on kiwifruit vines in the vineyards located in the Altınordu, Fatsa, and Perşembe districts of Ordu province in Turkey. The symptoms were associated with reddish-brown rots expanding from the root to the collar with sparse off-color foliage. Based on the percentage of the total infected samples across 18 vineyards, the most common oomycete species were (37.1%), (34.3%), (14.3%), (11.4%), and (2.9%). The morphological identification of isolates was confirmed based on partial DNA sequences containing the nuclear rDNA internal transcribed spacer region gene and the mitochondrial cytochrome oxidase subunit II gene. The optimum growth temperature and the optimum pH values of the five species ranged from 22.98 to 28.25°C and 5.67 to 8.51, respectively. Pathogenicity tests on the seedlings of kiwifruit cv. Hayward revealed significant differences in virulence among isolates. and isolates caused severe root and collar rot resulting in seedling death, while and isolates had relatively lower virulence. All spp. and isolates significantly decreased plant growth parameters (plant height, shoot and root dry weights, and root length); however, caused very mild symptoms and did not affect these parameters of growth. To our knowledge, this is the first study reporting , , and causing root and collar rot on kiwifruit not only in Turkey but also in the world.