RESUMEN

A new root-knot nematode (RKN) species, Meloidogyne karsseni n. sp., associated with sweet pepper from Mexico, and a population of M. paranaensis from Guatemala, are described using data from morphological, biochemical (isozyme enzymes), molecular, and phylogenetic analyses. Meloidogyne karsseni n. sp. can be morphologically diagnosed using the combined features of the second-stage juveniles, viz. body length (345 to 422 µm), a conical rounded head region, a post-labial annule lacking transverse striation, a thin stylet 11 to 12 µm long, rounded to oval and backwardly sloping knobs, dorsal gland orifice (DGO) at 5.2 to 6.0 µm from the knobs, a hemizonid just above the secretory-excretory (SE) pore, a tapering tail with finely rounded terminus and one or two very weak constrictions at hyaline tail tip; the female characters viz. oval-to-rounded perineal pattern with coarse striation on lateral sides around the anus, low dorsal arch with finer striations, and distinctly visible lateral lines; and the male characteristics viz. a rounded and continuous head, a post-labial annule without transverse striations, a robust stylet 20 to 24 µm long, rounded-to-oval and slightly backwardly sloping knobs, and a DGO at 2.4 to 2.9 µm from the knobs. In all the studied males of M. paranaensis, a characteristic sclerotization around the duct of SE-pore was also observed for the first time. Sequences of 18S, D2-D3 of 28S, and ITS of rDNA, and cox1 of mtDNA were generated for the two species, and in the phylogenetic trees based on these genes, both species appeared in the tropical RKN species complex clade.