Molecular Characterization of Phytoplasma-Associated Diseases in Squash (Cucurbita pepo L.) and Cucumber (Cucumis sativus L.) in Türkiye

Phytoplasmas are major pathogens responsible for severe losses in cucurbit production globally, yet their molecular characterization remains limited, particularly in Türkiye. During surveys conducted in Hatay, Türkiye, in 2024, phytoplasma-associated symptoms, including phyllody, virescence, sterility, general chlorosis, and stunting, were observed in squash (Cucurbita pepo) and cucumber (Cucumis sativus) plants. Total nucleic acid was extracted from 27 symptomatic plants using the CTAB method, and the presence of the pathogen was confirmed by PCR targeting the 16S rRNA gene using universal primers F1/R0 and F2n/R2. PCR analysis confirmed the presence of 16SrII-D subgroup phytoplasmas in symptomatic plants, with amplicon sizes of 1.4 kb and 1.2 kb, consistent with previous studies on phytoplasma diagnostics. BLAST analysis revealed that the sequences exhibited high similarity to Squash phyllody disease (SqPHY, PV056007) and Cucumber phyllody disease (CuPHY, PV056009) isolates, both belonging to the 16SrII-D subgroup. Furthermore, these isolates showed close genetic relationships with Yazd squash phyllody phytoplasma (KR822805) and Cucumber phyllody phytoplasma (MK453519) previously identified in Iran. Phylogenetic analysis confirmed the clustering of these isolates within the 16SrII-D subgroup, and these findings were further supported by virtual RFLP analyses. This study provides the first molecular evidence of 16SrII-D subgroup phytoplasmas infecting cucurbits in Türkiye, emphasizing their regional spread and the urgent need for vector control strategies.