Molecular and morphological characterization of Tylenchus zeae n. sp. (Nematoda: Tylenchida) from Corn (Zea mays) in South Carolina

Specimens of a tylenchid nematode were recovered in 2019 from soil samples collected from a corn field, located in Pickens County, South Carolina, USA. A moderate number of sp. adults (females and males) were recovered. Extracted nematodes were examined morphologically and molecularly for species identification, which indicated that the specimens of the tylenchid adults were a new species, described herein as n. sp. Morphological examination and the morphometric details of the specimens were very close to the original descriptions of and . However, females of the new species can be differentiated from these species by body shape and length, shape of excretory duct, distance between anterior end and esophageal intestinal valve, and a few other characteristics given in the diagnosis. Males of the new species can be differentiated from the two closely related species by tail, spicules, and gubernaculum length. Cryo-scanning electron microscopy confirmed head bearing five or six annules; four to six cephalic sensilla represented by small pits at the rounded corners of the labial plate; a small, round oral plate; and a large, pit-like amphidial opening confined to the labial plate and extending three to four annules beyond it. Phylogenetic analysis of 18S rRNA gene sequences placed n. sp. in a clade with and several spp., and the mitochondrial cytochrome oxidase c subunit 1 ( ) gene region separated the new species from and other tylenchid species. In the 28S tree, n. sp. showed a high level of sequence divergence and was positioned outside of the main clade.