|Shapiro Ilan, David|
Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2007
Publication Date: 3/1/2008
Citation: Nguyen, K.B., Shapiro Ilan, D.I., Mbata, G.N. 2008. Heterorhabditis georgiana n. sp. (Rhabditia: Heterorhabditidae) from Georgia, USA. Nematology. 10:433-448.
Interpretive Summary: Entomopathogenic nematodes are naturally occurring small round worms that are used as environmentally friendly biopesticides to control a variety of economically important insect pests. Because each nematode species (kind) can possess different abilities to control different insect pests, it is important to understand and characterize the diversity of nematode species in nature. There are currently approximately 12 species of entomopathogenic nematodes in the genus (group) Heterorhabditis that have been discovered and characterized. In this paper we report the discovery and description of a new entomopathogenic nematode species that is being named Heterorhabditis georgiana. The nematode was isolated from soil in a pecan orchard in Byron, GA. The new species differs from other nematodes in the same genus (group) based on its morphological and genetic characteristics. Based on a genetic and evolutionary analysis the new species appears to be most closely related to the nematode Heterorhabditis bacteriophora. Future research will determine if the new nematode has any special characteristics that may be particularly useful in biological pest control.
Technical Abstract: In a survey of entomopathogenic nematodes in Georgia, a nematode isolate of the genus Heterorhabditis was found. The nematode was collected from soil by the insect-baiting technique and maintained in the laboratory on last instar Galleria mellonella (L.) larvae. Morphological and molecular studies of the isolate showed that the nematode is a new species. Light and scanning electron microscopy, DNA characterization and phylogeny were used for this description. Heterorhabditis georgiana n. sp. is morphologically similar to H. bacteriophora and can be distinguished from these species mainly by male and female characters. Sixty percent of males have 3 pairs pf papillae; 40 % with 3 papillae on one side and 2 papillae on the other side. Tail conoid, slightly curved ventrally. The percentage of the gubernaculum to spicule length (GS%) is similar to that of H. mexicana (56) but higher than that of H. bacteriophora and species in indica group and the length of the spicule relative to anal body width (SW%) is lower than that of H. baujardi (171 vs 1182), H. indica (172 vs 187) and H. bacteriophora (1762 vs 174), but higher than that of H. amazonensis (172 vs 152), H. floridensis (172 vs 157) and H. mexicana (172 vs 167). The female can be differentiated from related species by its unique vulva pattern. In phylogenetic trees of ITS and D2D3 regions, the new species and H. bacteriophora form a monophyletic group. The new species has evolved five autapomorphic nucleotide character states, differing from its sister taxa H. bacteriophora at 29 aligned positions of ITS regions.