Phytopythium babaiaharii causing root rot on greenhouse cucumber

Root and crown rot is one of the most damaging diseases of greenhouse cucumber. In spring 2023, greenhouse cucumber with root and crown rot and decline symptoms were collected from different greenhouses in Kohgiluyeh & Boyer-Ahmad province. Infected tissues of the root were cut into approximately 5-6 mm pieces, and cultured on a semi-selective medium, CMA-PARPH without extra treatments. Purification of isolates was performed using the single-zoospore technique on WA. Fungal isolates were identified based on morphological characteristics and molecular data of cox1 gene and ITS- rDNA region. According to the morphological and phylogenetic analysis, all isolates were recognized as Phytopythium babaiaharii. Pathogenicity test were conducted using five isolates P. babaiaharii on Saman cultivar of cucumber under greenhouse conditions. Koch's postulates were completed and confirmed that P. babaiahari isolates were responsible for cucumber root and crown rots. To our knowledge, this is the first report that P. babaiahari associated with root rot of cucumber in Iran and probably in the world.