Detection of phytoplasmas of 16SrII group in two species of bindweed (Convolvulus spp.) affected by witches' broom disease

Paper ID : 1873-24IPPC (R3)

¹Department of Plant Protection, Shiraz University

²Sgiraz Unicersity

³Plant Protection Research Department, Fars Agricultural and Natural Resources Research and Education Center

⁴Plant Virology Research Center, Department of Plant Protection, Shiraz University

In December 2021, symptoms similar to phytoplasma diseases were observed in two species of bindweed, i.e., Convolvulus arvensis and Convolvulus virgatus in vegetable fields of Hormozgan province (Iran). C. arvensis (field bindweed) is a serious perennial weed that occurs throughout the temperate regions of the world. Another species, C. virgatus, is a shrub that grows around commercial fields and orchards. The main symptoms observed in the affected plants were witches' broom, plant stunting (shortened internodes), yellowing and little leaf in the C. arvensis plants and witches' broom and little leaf in the C. virgatus plants. To test possible association of phytoplasma with the symptoms observed, total genomic DNA was extracted from 0.2 g midribs using modified cetyltrimethylammonium bromide (CTAB) method. The samples were analyzed for phytoplasma DNA by direct-PCR using the phytoplasma universal primer pair Rl6mF2/R16mR1. Fragments of the expected size (1434 bp) were amplified by direct PCR in samples from symptomatic plant but not from symptomless plant or sterile distilled water as negative controls. A PCR products directly sequenced and deposited in the GenBank database under the following accession numbers: C. arvensis, OM974784; C. virgatus, OM975640. A BLAST search using sequenced fragments confirmed the phytoplasma infection and showed that the phytoplasmas associated with bindweed witches' broom (BWB) had 100 % nucleotide identity with the 16SrII phytoplasma group, Candidatus Phytoplasma aurantifolia. Virtual restriction fragment length polymorphism with iPhyClassifier software revealed that BWB phytoplasma in C. arvensis and C. virgatus belonged to 16SrII-C and 16SrII-D subgroups, respectively. There is a report regarding the association of 16SrXII group phytoplasma with field bindweed in Iran. To our knowledge, this is the first report of natural infection of C. arvensis to 16SrII-C subgroup phytoplasma and C. virgatus to 16SrII-D subgroup phytoplasma from Iran and most probably in the world. Phytoplasmas belonging to the 16SrII-C and D have been previously reported on several vegetable crops such as tomato, eggplant and bell pepper in Hormozgan. In view of the abundance of bindweed plants in or around the commercial fields, these weeds may serve as reservoir host for these phytoplasmas.

Little leaf; BWBP; 16SrII-C; 16SrII-D