Morphological and Molecular Characterization of Pratylenchus dakotaensis n. sp. (Nematoda: Pratylenchidae), a New Root-Lesion Nematode Species on Soybean in North Dakota, USA

Abstract

Root-lesion nematodes (<i>Pratylenchus</i> spp.) of the genus <i>Pratylenchus</i> Filipjev, 1936, are among the most important nematode pests on soybean (<i>Glycine max</i> (L.) Merr.), along with soybean cyst and root-knot nematodes. In May 2015 and 2016, a total of six soil samples were collected from a soybean field in Walcott, Richland County, ND and submitted to the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), USDA, ARS, MD for analysis. Later, in 2019, additional nematodes recovered from a greenhouse culture on soybean originally from the same field were submitted for further analysis. Males, females, and juveniles of <i>Pratylenchus</i> sp. were recovered from soil and root samples and were examined morphologically and molecularly. DNA from single nematodes were extracted, and the nucleotides feature of three genomic regions targeting on the D2-D3 region of 28S rDNA and ITS rDNA and mitochondrial cytochrome oxidase subunit I (<i>COX1</i>) gene were characterized. Phylogeny trees were constructed to ascertain the relationships with other <i>Pratylenchus</i> spp., and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to provide a rapid and reliable differentiation from other common <i>Pratylenchus</i> spp. Molecular features indicated that it is a new, unnamed <i>Pratylenchus</i> sp. that is different from morphologically closely related <i>Pratylenchus</i> spp., including <i>P</i>. <i>convallariae</i>, <i>P. pratensis</i>, <i>P. fallax</i>, and <i>P</i>. <i>flakkensis</i>. In conclusion, both morphological and molecular observations indicate that the North Dakota isolate on soybean represents a new root-lesion nematode species which is named and described herein as <i>Pratylenchus dakotaensis</i> n. sp.