Detection, Identification, and Molecular Characterization of a 16SrII-V Subgroup Phytoplasma Associated with Nicotiana plumbaginifolia

Nicotiana plumbaginifolia Viviani, commonly known as curl-leaved tobacco, is an annual herbaceous plant belonging to Solanaceae family. This plant is native to Mexico, South America, and parts of the Caribbean and has been reported to be present in Taiwan since 2006. In March 2021, N. plumbaginifolia Viviani, found in Yunlin County, Taiwan, was observed to have phyllody, virescence, and witches'-broom, which is consistent with the disease symptoms caused by phytoplasma infection. Samples of the healthy and symptomatic plants were collected for analysis of the causal agent associated with the diseased N. plumbaginifolia Viviani. Under transmission electron microscopy, the phytoplasma-like pleomorphic bodies were found in the sieve tubes of the diseased plants. The 16S ribosomal RNA (rRNA)-based phylogenetic analysis and the iPhyClassifier-based virtual restriction fragment length polymorphism study demonstrated that the phytoplasma identified in this study can be classified into the 16SrII-V subgroup, which is similar to the peanut witches'-broom phytoplasma, a 'Candidatus phytoplasma aurantifolia'-related strain. Further identification of SAP54/PHYL1 and SAP11 homologs in the phytoplasma explain the disease symptoms of phyllody, virescence, and witches'-broom observed in diseased N. plumbaginifolia Viviani. The discovery of new phytoplasma plant hosts has gained scientific importance in light of the attempt to unravel an efficient strategy to fight the rapid spread of this disease, which poses a threat to the agricultural sector and food security in Taiwan.