Detection and Molecular Characterization of Phytoplasma Associated with Phyllody Disease on Dimorphotheca pluvialis in Egypt

Abstract

During the spring of 2021-2022, imported grown African daisy (Dimorphotheca pluvialis L. Moench) plants (Family: Asteracae) exhibiting symptoms of phyllody phytoplasma, such as phyllody and virescence of flowers, and witches' broom, were observed in different gardens of Cairo governorate, Egypt. The disease was successfully transmitted experimentally through dodder (Cuscuta reflexa) to healthy periwinkle (Cantharanthus roseus) plants. The light and transmission electron microscopic examination revealed phytoplasma units in sieve tubes with a lot of deterioration of the cell components due to the phytoplasma infection. Nested polymerase chain reaction (nested-PCR) assay used as a key technique to identify the phytoplasma by amplifying products of 1250 bp using two pairs of primers; a universal primer pair (P1/P7) and (R16F2n/R16R2) as a specific primer pair. The Egyptian phytoplasma isolate (Dimo-Cairo) was registered with accession number “OQ676407.1” in the NCBI GenBank. MEGA sequence analysis software version 11 was used to generate the phylogenetic tree of Dimo-Cairo and to compare it with the other phytoplasma strains. The clustering of phytoplasma strains confirmed that Dimo-Cairo was associated with the 16Sr-II group (Candidatus Phytoplasma aurantifolia), and placed it close to stem curling and phyllody phytoplasma (16Sr-II-A subgroup), witches-broom phytoplasma and cactus witches-broom phytoplasma (16Sr-II-C subgroup) and Corchorus olitorius phytoplasma and Vicia faba stunting phytoplasma (16Sr-II-D subgroup). To our knowledge, this is the first report of a phytoplasma infecting Dimorphotheca pluvialis plants in Egypt