First Report of Root-Knot Nematode <i>Meloidogyne incognita</i> on Jute (<i>Corchorus capsularis</i>) in Taiwan

Jute (Corchorus capsularis L.) was once an important economic crop for fiber production in Taiwan. In addition to its fiber, jute leaves are rich in minerals and contain several bioactive compounds (Biswas et al. 2022). Today, "Taichung No. 1" (sweet jute), developed by the Taichung District Agricultural Research and Extension Station, has become a popular local vegetable and is primarily cultivated in the Taichung region (Peng 2024). In September 2023, soil samples were collected from the rhizosphere of jute plants in a field in Taiping District, Taichung City, Taiwan, during a field survey. A nematode population was established from a single egg mass and later used for species identification and pathogenicity tests. Perineal pattern analysis of eight mature females from the single female population show oval to rounded shapes with weak lateral lines. Dorsal arches are high and squarish, with smooth to wavy striae. Second-stage juveniles (J2s) are vermiform, possessing a slender tail that tapers to a rounded tip with a distinct hyaline region at the tail terminus. These morphological characteristics agree with the previous description of Meloidogyne incognita (Hunt and Handoo 2009). Molecular identification was performed by extracting DNA from approximately 1,500 J2s using GeneMark Tissue & Cell Genomic DNA Purification Kit (GeneMark, Taiwan). DNA amplification using the primer set Finc/Rinc, which specifically targets M. incognita (Zijlstra et al. 2000), yielded a 1,200 bp fragment, confirming the species identity. Further molecular analysis was conducted by amplifying 18S rDNA fragment, D2-D3 expansion segments of 28S rDNA, and a COII region on mtDNA using primer sets MelF/MelR, D2A/D3B, and TRNAH/MRH106, respectively (Stanton et al. 1997, Subbotin et al. 2006, Tigano et al. 2005). The 18S rDNA sequence (PV056137) obtained in this study exhibited 100% nucleotide identity with M. incognita isolated from the United States (KP901064). Similarly, the D2-D3 sequence (PV061583) was identical to M. incognita from the United States (KP901070), and the COII region sequence (PV056160) also showed 100% identity with M. incognita from the United States (NC024097). Phylogenetic trees based on these three gene sequences were plotted following Ye et al. (2021), revealing that the newly described root-knot nematode isolated from jute clustered with other M. incognita isolates. Pathogenicity tests were conducted on three-week-old, nematode-free jute plants that were directly germinated from seeds (Dali Horticulture Store, Taichung, Taiwan) and grown in 9 cm diameter pots filled with 200 cm3 of sterile peat moss/sand (1:1, W/W). Each plant (n=5) was inoculated with 2000 eggs (10 eggs/cm3), while control plants were treated with water only. Forty-five days after inoculation, jute plants inoculated with M. incognita had an average reproduction factor (final population/initial population) of 6.8. No galls were observed on the roots of the control plants. These results confirm that jute is a host of M. incognita. To our knowledge, this is the first report of M. incognita infecting jute (Corchorus capsularis cv. Taichung No. 1) in Taiwan.