Curcuma longa, commonly known as turmeric, is a rhizomatous, herbaceous perennial plant cultivated in warm, tropical and subtropical regions globally. It has been traditionally employed as an herbal medicine across China, India, Thailand, Malaysia, Indonesia, Japan, South Korea, and other countries to treat respiratory, digestive, circulatory, and skin diseases. Modern pharmacological research has demonstrated that C. longa exhibits antioxidant, anti-inflammatory, antitumor, antitussive, anti-diabetic, anticonvulsant, and hepatoprotective activities (Memarzia et al. 2022). Curcuma longa is the primary source of curcumin, a yellow-orange bioactive compound derived from its rhizomes. Curcumin is one of the principal ingredients in traditional Asian cuisine and curries, imparting their distinctive musky and sharp flavor (Ross 2024). In China, turmeric is widely cultivated in provinces and regions such as Sichuan, Yunnan, Fujian, Guangdong, and Taiwan (Tian et al. 2025). In July 2024, root galling was observed on C. longa in Sipsongpanna, Yunnan (21.8228° N, 100.3827° E), China. The incidence rate reached 100% in the 1334 m2 surveyed area. Egg masses and females were isolated from the roots of six diseased C. longa plants. The egg masses were incubated at 25 °C to obtain the second-stage juveniles (J2s). For J2s (n=20), body length= 509.26 ± 25.51 μm, body width 24.83 ± 1.74 μm, tail length= 54.95 ± 9.44 μm, stylet length= 12.52 ± 1.58 μm, distance from dorsal esophageal gland opening to the stylet knot (DGO)= 2.78 ± 1.44 μm; for females (n=20), pear-shaped, body length= 685.68 ± 81.41 μm, maximum body width= 462.84 ± 58.51 μm, stylet length= 12.42 ± 1.62 μm, DGO= 4.19 ± 0.87 μm, the perineum morphology is oval-shaped, with thick and smooth striations, the dorsal arch is high, and the overall texture is fine and dense, lacking obvious lateral lines. Morphometric analysis showed characteristics consistent with Meloidogyne enterolobii described by Yang and Eisenback (1983). Molecular identification was performed via amplifying 28S rDNA D2-D3 by the forward D2A (5’-ACAAGTACCGTGAGGAAAGTTG-3’) and reverse D3B (5’-TCGGAAGGAACCAGCTACTA-3’) primers, and ITS region by the forward 18S (5’-TTGATTACGTCCCTGCCCTTT-3’) and reverse 26S (5’-TTTCACTCGCCGTTACTAAGG-3’) primers, respectively (Subbotin et al. 2006; Vrain et al. 1992). D2-D3 and ITS sequencing (GenBank accessions PV747745 and PV746189) revealed 99.85 % - 100 % similarity to M. enterolobii (OR149157.1 and OL663829.1) (n=6). Phylogenetic relationships among taxa were analyzed using neighbor-joining method. The phylogenetic tree constructed based on the D2-D3 region of the 28S rDNA and ITS region sequences, revealed that the root-knot nematodes of C. longa clustered on the same branch as M. enterolobii, clearly distinguishing them from other sequences. To fulfill Koch’s postulates, about 1000 J2s per plant were inoculated onto 15 healthy C. longa plants in pots, while 15 control plants without nematodes. Sixty days post-inoculation, the inoculated plants exhibited typical root gall formation, while the control plants were devoid of any root galls. The gall index was evaluated based on the number of galls rated on a 0 to 5 scale (Brito et al. 2020). The average GI of inoculated C. longa was 3.33 ± 0.58, final number of eggs (Pf) was 158.33 ± 28.47, eggs per gram of freshroots (gfr) was 54.93 ± 6.03, and a reproduction factor (RF=Pf/Pi) was 1.69 ± 0.40 (n=20). To our knowledge, this is the first report of M. enterolobii infestation in Yunnan Province and the first formal record of its infection on C. longa. The results provide a scientific basis for the prevention and management of root-knot nematode diseases.
Xian et al. (Fri,) studied this question.