First Recorded Parasitism of <i>Solanum muricatum</i> by <i>Cuscuta chinensis</i> in China

The genus Cuscuta (dodder) comprises numerous obligate holoparasitic plant species widely distributed in China and damaging natural and agricultural vegetation (Albert et al. 2021). Among them, Cuscuta chinensis has a broad host range on herbaceous and woody plants (Zhang et al. 2018). Although C. chinensis is well documented on medicinal plants, shrubs, and field crops, there have been no previous records of its parasitism on Solanum muricatum, an economically important Solanaceous fruit crop in Yunnan Province. In 2024, field surveys in Shilin County, Kunming, Yunnan Province (24°49′31″N, 103°16′02″E), within a mixed fruit–vegetable production area of approximately 1.5 ha, revealed reduced vegetative vigor and reproductive output in several S. muricatum plants. About 25 plants were inspected, and one plant was parasitized by dodder, corresponding to a 4% incidence within the surveyed area. Affected plants showed leaf chlorosis, wilting, reduced vigor, and smaller fruits, symptoms atypical of common pepino diseases in the region. The parasite had yellow, leafless, filamentous stems tightly twining around host stems and petioles, forming dense coils and producing conspicuous haustoria at the nodes. These traits, together with umbellate inflorescences bearing 2-8 small white flowers with a pentamerous corolla, correspond to the diagnostic morphology of C. chinensis (Zhang et al. 2018). To confirm species identity, genomic DNA was extracted from dodder stems and subjected to Illumina high-throughput sequencing. The complete chloroplast genome was assembled and annotated using the Plant Genome Annotation pipeline (Qu et al. 2019), yielding a circular genome of approximately 86,800 bp (GenBank accession PQ585822). BLAST analysis revealed 99.8% sequence similarity and 100% query coverage with a reference C. chinensis chloroplast genome (MH780079). Phylogenetic analyses further validated the taxonomic placement. Maximum likelihood (1,000 bootstrap replicates) and Bayesian inference (2,000,000 MCMC generations, sampling every 1,000 generations) consistently placed our specimen within the C. chinensis clade with strong support. The agreement between morphology, chloroplast genome data, and phylogeny confirmed that the dodder collected in Shilin County is C. chinensis. Voucher specimens of the dodder and the affected S. muricatum host were deposited in the Herbarium of the College of Horticulture and Landscape, Yunnan Agricultural University (specimen no. 20240002). This is the first documented case of C. chinensis parasitizing S. muricatum in China. This new host-parasite association has implications for pepino melon cultivation, as the crop is increasingly adopted as a high-value horticultural species in Yunnan. Even at low incidence, the occurrence of C. chinensis on S. muricatum raises concerns about potential spread, especially in agroecosystems with alternative herbaceous hosts. This finding also expands the known host range of C. chinensis and improves understanding of the ecological adaptability and parasitic strategies of dodder species.