Diversity of Plant-Parasitic Nematodes of the Genus Pratylenchus (Nematoda: Pratylenchidae) in California: Descriptions of Two New Species and Insights from Phylogenetic Analyses

Root-lesion nematodes of the genus Pratylenchus are among the most economically significant plant-parasitic nematodes worldwide. During nematological surveys conducted in natural and agricultural ecosystems in California, several known species, P. bolivianus, P. hippeastri, P. pinguicaudatus, P. scribneri, P. thornei, and P. vulnus, as well as two undescribed species, P. chizhovi sp. n. and P. gracilis sp. n., were recovered. Pratylenchus chizhovi sp. n. is characterized by a slightly offset lip region with three annuli narrowing anteriorly, a short stylet (14.5–17.0 µm) with rounded knobs, a lateral field with four incisures, a spherical spermatheca lacking sperm, a vulva with somewhat prominent lips, a subcylindrical tail with a truncate-rounded, smooth terminus, and unknown males. Pratylenchus gracilis sp. n. is characterized by a lip region offset with three annuli narrowing anteriorly, a short stylet (15–18 µm) with rounded knobs, a lateral field with four incisures, an oval to rounded spermatheca containing some sperm cells, a vulva with somewhat prominent lips, a subcylindrical tail with a rounded, smooth terminus, and males present. Phylogenetic relationships of California Pratylenchus species and other members of the genus were inferred using 18S rRNA, D2–D3 of 28S rRNA, and the mitochondrial COI gene sequences. This study provides an updated assessment of Pratylenchus species diversity in California, highlighting both previously described taxa and newly discovered species.