First Report of ‘Candidatus Phytoplasma aurantifolia’ Associated with the Invasive Weed Eclipta prostrata in Taiwan

Abstract

Eclipta prostrata (L.), commonly known as false daisy of the family Asteraceae, is an erect or prostrate annual herb that grows 5 to 45 cm tall. It is widespread mainly in tropical and subtropical regions like India, China, Taiwan, Thailand, and Brazil (Chung et al., 2017). E. prostrata has very wide medicinal properties accounted by several phytochemicals like thiophene derivatives, steroids, flavonoids, and polypeptides (Feng et. al., 2019). It is also used as a traditional herbal medicine for the treatment of bleeding, hemoptysis and itching, hepatitis diarrhea, and even hair loss (Timalsina et al., 2021). In September 2021, E. prostrata displaying branch proliferation and phyllody symptoms with about 30% (6 were symptomatic and 14 were healthy) incidence rate was observed in Mailiao, Yunlin, Taiwan where phytoplasma disease is permeating and has affected many crops and non-crop species including peanut, mungbean, curl-leaved tobacco, false amaranth, etc. Compared to healthy E. prostrata bearing white ray florets and cream or dull white disk florets, symptomatic ones developed phyllody which is more pronounced on the severely infected ones. Further examination by transmission electron microscope revealed a pleomorphic (circular, elliptical, and bell-shaped) phytoplasma-like organisms accumulated in the sieve elements of the symptomatic leaves. Phytoplasma infection was further confirmed by nested polymerase chain reaction using universal primers P1/P7 (carried out for 12 cycles), followed by R16F2n/R16R2 (carried out for 35 cycles) on the genomic DNA extracted by Plant Genomic DNA Purification Kit (DP022-150, GeneMark) (Lee et al. 1993). Results revealed that the conserved 16S rRNA gene with a 1.2 kb fragment size was amplified only by the symptomatic samples. Furthermore, western blotting was done using the polyclonal antibody raised against the immunodominant membrane protein (Imp) of peanut witches’-broom (PnWB) phytoplasma, a ‘Candidatus Phytoplasma aurantifolia’ in Taiwan that belongs group to 16SrII (Chen et al. 2021). Consistent with the nested PCR, only the symptomatic samples revealed a specific Imp signal with a size of 19 kDa. To classify the phytoplasma associated with the symptomatic E. prostrata, the DNA sequence (No. OM397418) of the P1/P7 primer pair-amplified DNA fragment was obtained using P1 and a nested primer (5’-GGGTCTTTACTGACGCTGAGG-3’), which shares 100% identity with that of GenBank accession NZ_AMWZ01000008 (complement [31109 to 32640]) of PnWB phytoplasma. Further analysis of the virtual RFLP pattern of OM397418 by iPhyClassifier confirmed that the phytoplasma identified in the symptomatic E. prostrata belongs 16SrII-V subgroup. To the best of our knowledge, this is the first report of phytoplasma disease in E. prostrata associated with the ‘Ca. P. aurantifolia’ in Taiwan.

Detection, Identification and Molecular Characterization of the 16SrII-V Subgroup Phytoplasma Strain Associated with Pisum sativum and Parthenium hysterophorus L.

“…The epidemiological cycle of phytoplasma involves plants and insects. More than parthenium weed, several invasive weeds, e.g., Eclipta prostrata , Ixeris chinensis , Digera muricata and Nicotiana plumbaginifolia, were also found to be infected with the 16SrII-V subgroup phytoplasma strains in Mailiao, Yunlin, Taiwan [ 43 , 44 , 45 , 46 ]. Thus, identification of insect vectors is required to make informed decisions in order to manage the phytoplasma diseases, for they pose a potential threat to Taiwan’s agricultural industry and food security.…”