Phytoplasma Disease of Jasminum sambac L. in Egypt: Molecular Identification, Host Responses, and Pathobiological Implications

In September 2023, yellow blotches, slight leaf malformation, stunting, flower color alteration and thickened bark above the phloem interruption point symptoms, as a virus or phytoplasma-like infection, were observed on Jasminum sambac L. plants in Ismailia and Giza governorates, Egypt. Collected samples were tested by direct ELISA, using the available antisera specific for AMV, PVY, ToRSV, PVX, PLRV, TMV, CMV, ToMV, and TYLCV; however, all tests were fruitless (negative). To diagnose these symptoms as phytoplasma-associated, Dienes' stain was used, followed by examination under incident light microscopy of the Jasminum sambac L. plants. Blue-stained areas were clearly obcerved in the infected phloem tissues, indicating the presence of phytoplasma while we did not notice those blue areas in the healthy phloem (control). Furthermore polymerase chain reaction (PCR) was used successfully with positive results. The amplified products of nested PCR were purified and then sequenced. Sequencing and phylogenetic analysis were performed to identify the detected phytoplasmas. The partial sequence was conducted by the NCBI GenBank database with accession number PP970365, and its definition was 'Jasminum sambac L.' phytoplasma clone PVIDL 16S ribosomal RNA gene, partial sequence with Taxonomy ID: 2030933. Phylogenetic analysis showed a high similarity (97%) with Candidatus Phytoplasma sp.16Sr-IID isolates. Phytoplasma affects plants through different mechanisms, and so, the extent of the effect of phytoplasma on individual Jasminum sambac L., plants was studied in terms of anatomical and biochemical studies to demonstration the relationship between plant defense and effect of phytoplasma on histological and cytological changes, and subsequently, biochemical changes. This study aims to provide the first documentation of the morphological symptoms of phytoplasma infection of Arabian jasmine (Jasminum sambac L.) by the plesiidae insect. This plant is cultivated in Egypt for ornamental, aromatic, and medicinal purposes. The study also aims to achieve molecular confirmation of phytoplasma infection using polymerase chain reaction (PCR), deposit the extracted sequence in GenBank, and characterize the phytoplasma strain and its evolutionary relationships. Furthermore, it seeks to determine the plant's defense mechanisms and resistance, the effects of the disease on the plant, and its pathological indicators, thus contributing to the integrated management of this disease in ornamental plants in general and jasmine in particular.