Molecular Characterization of Different Phytoplasma Isolates Affecting New Hosts from Ornamental Plants in Egypt

Abstract

During 2021-2022, Phytoplasma-like infection symptoms were seen on various ornamental plants such as Euphorbia milii, Catharanthus roseus, Duranta erecta, and Carpobrotus edulis in four Egyptian governorates, Mansoura, Giza, Ismailia, and Matrouh. Natural symptoms associated with phytoplasma infections include leaf yellowing, leaf deformation, and plant stunting. Dienes' staintreated hand-cut sections examined under a light microscope revealed blue patches around the affected plant regions. The primer pairs P1/P7 and R16F2n/R16R2 were used in PCR and nested-PCR assays to detect and identify phytoplasma in diseased ornamental plant samples. The amplified products of nested PCR were purified and then sequenced. The sequences were submitted to the GenBank database under the accession numbers OP723297, OP730893, OP723296, and OP723295, which were named EGY-SEAM1, EGY-SEAM2, EGY-SEAM3, and EGY-SEAM4, respectively. According to a comparative analysis using the iPhyClassifier database at the level of groups/subgroups with 41 references, sequences showed that one phytoplasma isolate was classified as related to (AF510323) Aconitum proliferation phytoplasma (16SrI-A) in Lithuania (99.7%), another isolate of phytoplasma belongs to the 16SrI-B type, the closest relative (98.8%) to Potato purple top phytoplasma (EU333396) in Russia, and other two isolates were similar or identical to the
16SrII-D type (98.6% or 100%) to Papaya yellow crinkle phytoplasma (Y10097) in Australia. In conclusion, the findings may suggest that Catharanthus roseus or Carpobrotus edulis plants in Egypt could serve as new hosts for the 16SrI group, subgroup A or B, as well Euphorbia milii and Duranta erecta plants for the 16SrII group, subgroup D. The presence of phytoplasma-related diseases in different Egyptian governorates shows the existence of numerous new hosts that may affect the production of several vegetables crops.