Background Entomopathogenic nematodes (EPNs) are evidently a useful nematode group for the biocontrol of insect pests. It is well known that efficacy of different EPN strains, even belonging to the same species, can be significantly varied in different localities. Therefore, exploring EPNs and testing their efficacy in various ecological regions is of crucial importance to find out more efficient EPN strains. On the other hand, this practice is also needed to enhance the knowledge on diversity and distribution model of EPNs over the world. Results In this study, a species belonging to the genus Steinernema, S. surkhetense, has been characterized for the first time in Vietnam based on morphological and molecular characterizations. Morphological characterizations of infective juveniles, the first and second-generation adults, and molecular characterization of D2-D3 expansion segment of 28S rRNA region were given. Molecular phylogeny of the genus Steinernema was also provided. In addition, the study showed that the lethal efficacy of this local strain to larvae of Galleria mellonella L. was relatively higher than other reported EPN strains in Vietnam. Conclusions The Vietnamese EPN population found in this study was determined to be conspecific with S. surkhetense, revealed its new distribution in Vietnam. Besides, detailed morphological and molecular characterizations of it was provided with small variations compared to other populations in the world, and its relatively high lethal efficacy on larvae of G. mellonella implied that this strain can be potentially a useful strain for biological control of insect pests.

Meloidogyne incognita is considered the most damaging and common root-knot nematode causing serious damage to numerous host plants worldwide. During a survey of nematodes in Vietnam, 1106 samples from 22 different plant species were collected. Meloidogyne incognita was recorded on 13 of 22 host plants. Four populations of M. incognita from four host plants were chosen for comparison and confirmation of their morphological, morphometric, and molecular characteristics. Genetically-based phylogenetic trees were developed to show relationships among root-knot nematodes. Molecular barcodes of four gene regions, including ITS, D2-D3 of 28S rRNA, COI, and Nad5 mtDNA, integrated with morphological and morphometric data were used as reliable references for molecular identification of M. incognita. Our analyses indicated that tropical root-knot nematodes are very similar in characterization of ITS, D2-D3 of 28S rRNA and COI regions. However, these gene regions can be used to separate tropical root-knot nematode group from other groups. On the other hand, the analysis of Nad5 mtDNA and multiplex-PCR with specific primers can be used to distinguish tropical species.