First report of the cactus cyst nematode, Cactodera cacti, infecting dragon fruit (Selenicereus undatus) in Hainan Province, China

Dragon fruit (Selenicereus undatus) is a commercially important tropical fruit widely cultivated in Southeast Asia. During a nematode disease survey in Danzhou County, Hainan Province, China, cyst nematodes were recovered from the rhizosphere soil and roots of dragon fruit plants exhibiting poor growth. Morphological and morphometric analyses of cysts and second-stage juveniles matched the original and subsequent descriptions of Cactodera cacti. Molecular characterization, based on sequences of the ITS rRNA, the D2–D3 expansion segments of 28S rRNA, and the mitochondrial cytochrome c oxidase I (COI) gene, confirmed the species identity as C. cacti. Phylogenetic analysis using the Neighbor-Joining method revealed that this population clustered closely with known C. cacti populations from the USA, Vietnam, and Taiwan, China. A pathogenicity test on dragon fruit seedlings yielded a reproduction factor (Rf) of 11.6, indicating high pathogenicity. This is the first report of C. cacti infecting dragon fruit in Hainan, highlighting a potential threat to regional dragon fruit production.