Morphological and molecular characterisations of Hirschmanniella mucronata associated with rice from Red River delta in Vietnam

Rice production is threatened by various pathogens, including plant-parasitic nematodes like those from the genus Hirschmanniella, which can significantly reduce its yield. This study focuses on the morphological and molecular characterisations of Hirschmanniella mucronata associated with rice cultivation in Red River Delta in Vietnam. Morphological analysis revealed that while the three populations of H. mucronata from different regions exhibited some morphometric differences, their overall morphology was consistent with previous data. Morphometric variations were observed and confirmed by Cluster and MDS (Multidimensional Scaling) analyses, indicating possible regional or environmental influences on their morphology, emphasising the need for integrated approaches for accurate nematode identification. Molecular analyses based on D2–D3 of 28 S region identified three distinct clades within H. mucronata sequences. The Vietnamese sequences showed high identity (99.0–99.7% in 28 S and 99.88–99.97% for 18 S regions) to those from Cambodia. However, in 28 S tree, Chinese sequences (KR780066 and MW424471) displayed significant genetic divergence from all other sequences of H. mucronata, suggesting potential cryptic speciation or misidentification. The genetic diversity observed within H. mucronata underscores the complexity of its taxonomy and highlights the importance of using comprehensive identification methods. Additionally, our analysis showed that 18 S sequences of H. mucronata from Vietnam are 100% identical to each other and highly identical to those of H. mucronata available in GenBank (KP179330 and KP179332), differing by only 1–2 bp (99.88–99.97% identity). This study provides robust evidence for the presence of H. mucronata in Vietnam and calls for a reconsideration of previous identifications. This study also provided, for the first time, molecular data and SEM pictures of H. mucronata from Vietnam, facilitating the identification of this species.