Emerging pest of root-knot nematode, Meloidogyne enterolobii, on mulberry in Vietnam
Mulberry is an important crop contributing to economic development in many localities. Lam Dong province has the largest mulberry-growing area in Vietnam, covering approximately 9,800 hectares, with an estimated annual leaf production of around 247,000 tons, cocoon production of about 16,000 tons, and silk fiber production exceeding 2,000 tons. The province is home to approximately 16,000 farming households engaged in mulberry cultivation and silkworm rearing. However, root-knot nematodes have recently emerged as a new pest affecting mulberry in Lam Dong. Between 2020 and 2021, the disease spread, causing damage to 425 hectares in Da Huoai and Da Teh districts. The rapid and widespread mortality of mulberry plants necessitated identifying the cause to implement timely control and prevention measures.
Figure 1: Widespread mulberry dieback in Lam Dong
Field observations of mulberry plants in Lam Dong indicated symptoms associated with root-knot nematodes (Meloidogyne spp.). This group of nematodes is one of the most polyphagous and damaging plant-parasitic nematodes globally. These endoparasitic nematodes can infect nearly all higher plants and have a nearly worldwide distribution. Accurate species identification within this group requires advanced techniques due to morphological overlap among closely related Meloidogyne species. Species confirmation relies on molecular techniques.
Morphological and morphometric analyses of root-knot nematode populations from Da Teh and Lam Ha districts (Lam Dong) were compared with known Meloidogyne species worldwide, revealing close similarities with M. enterolobii. Key characteristics such as the perineal pattern, phasmid position, lateral field, female tail tip, male and second-stage juvenile (J2) measurements (Figure 2A-E) closely matched M. enterolobii. Although most morphological indices aligned with previously described M. enterolobii populations, some morphometric values overlapped with M. incognita, necessitating molecular confirmation. Sequence and phylogenetic analyses of D2-D3/28S rRNA and 18S rRNA gene regions (GenBank accession numbers: OR889633, OR889634, OR896547) revealed 99-100% sequence similarity with M. enterolobii populations from ornamental plants and golf course grass in North Carolina (USA), chili (Thailand), and poinsettia (Taiwan, China). These sequences were distinctly separate from M. incognita, confirming that the root-knot nematode population affecting mulberry in Lam Dong belongs to M. enterolobii.
Additionally, pathogenicity tests following Koch’s postulates showed that after 90 days of inoculation, the reproduction factor (RF) of M. enterolobii was 11.5, and infected plants exhibited leaf yellowing and severe root galling, mirroring symptoms observed in the field. This confirms that M. enterolobii has a high pathogenicity on mulberry, similar to reports from other countries where this species is classified as a quarantine pest.
Figure 2: Morphology and artificial inoculation of root-knot nematode Meloidogyne enterolobii on mulberry
This study highlights the importance of combining molecular biology, morphology, and biology in assessing the pathogenic potential of nematodes on crops. Additionally, it contributes to knowledge on species diversity, molecular and morphological characteristics, distribution, and new host records for M. enterolobii. Most importantly, it provides essential information for pest surveillance, management strategies, and timely intervention in plant protection, ensuring sustainable agricultural development in Vietnam.
The findings of this study have been published in Plant Disease, a prestigious ISI-indexed journal with an Impact Factor (IF) of 4.4, supported by the Nafosted Fund: Duc Nguyen, H., Linh Le, T. M., Tien Nguyen, H., Duyen Nguyen, T., Hoa Pham, T., Phap Trinh, Q., & Nguyen, N. C. (2024). First Report of the Damaging Pest Meloidogyne enterolobii Parasitizing Mulberry (Morus alba) in Vietnam. Plant Disease, 108(5), 1406. https://doi.org/10.1094/PDIS-12-23-2727-PDN
Translated by Phuong Huyen
Link to Vietnamese version
