Morphological and molecular characterisations of <i>Aphelenchoides vinhphucensis</i> sp. n. associated with rice from Vietnam

The genus <i>Aphelenchoides</i> Fischer, 1894, encompasses nearly 200 species with significant ecological and economic importance, yet its taxonomy remains complex due to morphological similarities among species and limited molecular data. In this study, we describe a new species, <i>Aphelenchoides vinhphucensis</i> sp. n., collected from the rhizosphere of rice (<i>Oryza sativa</i> L.) in Vinh Phuc Province, Vietnam. The new species is distinguished by its morphological characteristics, including a slender stylet (9.6-12.7 μm), distinct lateral fields with four lines, a conical tail with a pointed mucro, and a well-developed post-uterine sac. Males feature three pairs of caudal papillae and arcuate spicules. Scanning electron microscopy provided detailed insights into surface features, complementing light microscopy observations. Molecular analyses of the D2-D3 regions of 28S rRNA and 18S rRNA supported the distinct phylogenetic placement of <i>Aphelenchoides vinhphucensis</i> sp. n., differentiating it from closely related species. Bayesian phylogenetic analysis confirmed its divergence, contributing to our understanding of biodiversity of the genus <i>Aphelenchoides.</i> This integrative approach highlights the importance of combining classical morphological methods with modern molecular tools for accurate species identification. The discovery of <i>Aphelenchoides vinhphucensis</i> sp. n. underscores the nematode diversity in Vietnam, especially those associated with rice cultivation.