A survey of entomopathogenic nematodes in Vietnam yielded several Heterorhabditis isolates. The majority belonged to H. indica; their morphometrics are given in this paper. Three isolates collected in forests in Backan, Ninhbinh and Kontum provinces, Vietnam are here described as a new species Heterorhabditis baujardi sp. n. The new species is distinguished from the other ten valid Heterorhabditis species by a combination of morphological, morphometrical, and DNA characters. Heterorhabditis baujardi sp. n. is morphometrically similar to H. indica, but can be separated from this species by the shape of the gubernaculum and the number of normal pairs of genital papillae. The gubernaculum of H. baujardi sp. n. with the proximal end ventrally curved resembles that of H. bacteriophora. Heterorhabditis baujardi sp. n. can be separated from this latter species by a shorter body length of infective juveniles and longer spicules, longer gubernaculum, and a higher spicule length to anal body diameter ratio of males. The canonical discriminant analysis of morphometrical characters of both infective juveniles and males failed to discriminate Heterorhabditis baujardi sp. n. from H. indica. However, the new species was easily distinguished from H. downesi, H. marelatus, H. megidis and H. bacteriophora. Heterorhabditis baujardi sp. n. was slightly separated from H. bacteriophora by variables of the infective juveniles, but was clearly distinguishedby variables of the males. Cross-breeding tests using isolates of the new species and H. indica did not yield fertile progeny. Analysis of the ITS1 sequence of rDNA of H. baujardi sp. n. revealed substantial differences with other known ITS1 Heterorhabditis sequences. Phylogenetic relationships between Heterorhabditis species and the usefulness of morphological and molecular characters for identi cation of species from this group are discussed.

A new entomopathogenic nematode, Steinernema huense sp. n., belonging to the carpocapsae group, was recovered in Bach Ma National Park (Thua Thien Hue province) Vietnam. Steinernema huense sp. n. infective juveniles are characterised by short body length of 527 (444-571) p m, distance from anterior end to excretory pore of 43 (38-46) pm, anterior end to end of pharynx of 116 (103-129) pm; tail length of 50 (43-56) pm, D% = 37 (34-39) and E% = 85 (79-93), H% = 44 (39-52) and in having six ridges (i-e., seven lines) in the lateral field. For first generation males, the diagnostic characters include the spicule length of 67 (60-72) pm; D% = 48 (41-61); and GS% = 76 (68-81). Both generations possess a minute filamentous mucron, which can be rudimentary in the first generation, and 23 genital papillae. Spicules are finely curved, brownish and slender with a prominent rostrum. First generation females have a non-protruding, symmetrical vulva, with double flapped epiptygma. The tail of mature females is obese with a short conical tip (peg) lacking minute protuberances, and post-anal swelling not developed. The new species is further characterised by sequences of ITS and D2-D3 regions of the ribosomal DNA. According to molecular data, the symbiotic bacterium of S. huense sp. n. is closely related to Xenorhabdus stockiae.

Ginger (Zingiber officinale Roscoe) and long coriander (Eryngium foetidum L.) are commonly grown and used as important spices and medicinal plants in Vietnam. Our study recovered for the first time one of the most damaging tropical root-knot nematodes, Meloidogyne javanica, associated with these plants in the Western Highlands of Vietnam. In this study, M. javanica was characterized based on morphology and molecular characterization of D2-D3 fragment of 28S rRNA, ITS, and Nad5 mtDNA regions. The identification of this species was done based on a combination of morphology, multiplex-PCR with specific primer, network haplotype analysis, and PPNID program.

Panax vietnamensis Ha et Grushv. is a precious medicinal species native to the tropical forests of Vietnam. Due to habitat loss and over-harvesting, this species is endangered in Vietnam. To conserve the species, we investigated genetic variability and population structure using nine microsatellites for 148 individuals from seven populations across the current distribution range of P. vietnamensis in Vietnam. We determined a moderate genetic diversity within populations (HO = 0.367, HE = 0.437) and relatively low population differentiation (the Weir and Cockerham index of 0.172 and the Hedrick index of 0.254) and showed significant differentiation (P < 0.05), which suggested fragmented habitats, over-utilization and over-harvesting of P. vietnamensis. Different clustering methods revealed that individuals were grouped into two major clusters, which were associated with gene flow across the geographical range of P. vietnamensis. This study also detected that ginseng populations can have undergone a recent bottleneck. We recommend measures in future P. vietnamensis conservation and breeding programs.

Two new species of Steinernema (Rhabditida), Steinernema loci sp. n. and S. thanhi sp. n., were isolated from beach soil in Thanhhoa and Hatinh provinces in the northern part of Vietnam. A combination of morphological, morphometric and rDNA-RFLP features indicated the distinctness of both species from other Steinernema spp. Diagnostic characters of Steinernema loci sp. n. include: total body length (896-1072 ¹m), distance from anterior end to excretory pore (EP D 71-86 ¹m), tail length (66-83 ¹m), lateral eld in mid-body with eight ridges (nine distinct lines) and rounded, broad and smooth anterior end of the third stage infective juvenile; rst generation males were characterised by body width, spicule length and the ratio spicule length : anal body width (SW). Diagnostic characters of Steinernema thanhi sp. n. third stage infective juveniles include: total body length (720-960 ¹m), EP (68-84 ¹m), tail length (52-72 ¹m), lateral eld in mid-body with eight ridges (nine distinct lines) and rounded, broad and smooth anterior end. Spicule length, ratio SW and arrangement of genital papillae characterised the rst generation males.