First Report of Dodder (<i>Cuscuta chinensis</i>) Parasitizing <i>Hedera nepalensis</i> var. <i>sinensis</i> in Yunnan, China

Dodder (Cuscuta spp.), particularly the species Cuscuta chinensis, is a parasitic weed known for its ability to infest a broad spectrum of plant species, thereby significantly affecting the stability and functionality of native ecosystems (Zhang, Xu et al. 2021). This species exhibits a remarkable capacity to parasitize a wide range of host plants, encompassing both woody and herbaceous species across various botanical families, such as Fabaceae, Asteraceae, Polygonaceae, and Rosaceae (Ikeue, Schudoma et al. 2015, Cirocco, Facelli et al. 2020, Dawson, Musselman et al. 1994). However, the parasitic climbing plants of the genus Cuscuta have not yet been extensively documented in scientific literature. In June 2023, C. chinensis was observed parasitizing Hedera nepalensis var. sinensis in Changchong Mountain (102°42'55″N, 25°7'01″E, elevation 1901m), Kunming City, Yunnan Province, China. H. nepalensis var. sinensis is a woody evergreen perennial vine that retains its leaves year-round greenery in landscaping. Field observations recorded the invasion of the lignified stems of H. nepalensis var. sinensis by the parasitic vine C. chinensis, showcasing the clear vascular infiltration visible to the naked eye. Furthermore, the foliar tissues of the host display evident symptoms of chlorosis, desiccation, and in certain instances, abscission. We set up 20 quadrats, each measuring 1 m2, within a 2-hectare to conduct an extensive ecological survey aimed at determining the host preference of C. chinensis for the populations of H. nepalensis var. sinensis within this 2-hectare range. The study entailed a meticulous examination of the local flora, with a particular focus on arboreal species and pteridophytes in the vicinity. The results of the survey indicate that C. chinensis exhibits a marked preference for climbing plants as its primary hosts within the surveyed area. We extracted total DNA from dodder stems using the CTAB method (Doyle, J, et al. 1991). Whole plasma was sequenced using genome skimming (Qu et al. 2019). The length of the chloroplast genome is 86,972 bp. The obtained sequence was deposited in GenBank (accession number: PP796631), and BLAST analysis was performed to confirm the species identity as C. chinensis (99.95%, Species accession numbers: MH780079). Phylogenetic analyses have demonstrated that the observed Cuscuta species exhibits the highest degree of genetic similarity and the least divergence in branch lengths (0.00015 and 0.00025, respectively) with the established the C. chinensis, and this relationship is supported by a bootstrap confidence value of 100%. Thus, this dodder specimen discovered in this ecological survey was identified as C. chinensis based on evidence from morphology, molecular biology and phylogenetics. Herbarium specimens of C. chinensis were collected and are now preserved in the repository of the College of Horticulture and Landscape, Yunnan Agricultural University (No. 202311010C). To the best of our knowledge, this is the first documentation of C. chinensis infecting H. nepalensis var. sinensis, marking a unique instance of parasitic behavior exhibited by C. chinensis on a global scale across liana species.