Morphological and molecular description of Ditylenchus baoqingensis n. sp. (Rhabditida: Anguinidae) from Chinese cabbages (Brassica rapa) in China.

A new species of the genus Ditylenchus-like nematodes, was recovered from the rhizosphere surrounding Chinese cabbage (Brassica rapa subsp. pekinensis) roots in Baoqing county, Heilongjiang province, China. The species,Ditylenchus baoqingensis n. sp., is characterized morphologically by slender females with four lateral field incisures, a delicate and short stylet (7.2-8.0 µm) with rounded knobs, a long pyriform basal pharyngeal bulb abutting the intestine, a well-developed hemispherical cardia, a posterior vulva (V = 79.1-82.4), a short and empty post-uterine sac (11.7-23.2 µm), a short and straight genital branch, and a long conical tail with a rounded terminus. Males resemble females in general morphology, possessing spicules 16.8-17.8 µm in length and a leptoderan bursa extending over approximately half the tail length. Molecular characterization was performed using the internal transcribed spacer (ITS) region and the 28S rRNA D2-D3 expansion segments. Phylogenetic analyses based on both ITS and D2-D3 sequences support the placement of D. baoqingensis n. sp. as a distinct lineage, closely related to Ditylenchus valveus and Ditylenchus israelensis within the genus.