The first morphological and molecular characterization of plant-parasitic nematodes in Rwanda, with description of new species of Pratylenchus

Abstract

Twenty one plant-parasitic nematodes genera representing eleven families were recovered from 41 soil and root samples collected from 15 crops in six different Rwandan agricultural zones. Morphologically and molecularly characterization was carried out on five populations of Scutellonema paralabiatum, three populations of S. brachyurus, 2 populations of S. cavenessi, one unidentified Scutellonema species, 2 populations of Pratylenchus penetrans and P. goodeyi. Special emphasis was given to the description and characterization of a new Pratylenchus species. Pratylenchus n. sp. can be distinguished from the other Pratylenchus species by combination of the following features of female: body slender with medium size (469-600μm); body cuticle in lateral field with four lines at pharynx level and posteriorly at level of phasmid in tail region, six to eight lines at mid body and six to ten at vulva region; the lateral lines at vulva region showing a slight oblique pattern; ridges in general smooth except in some specimens at phasmid level where they are annulated. Labial region with 3 lips annuli, the last lip annulus thicker than the first two and offset by a deep constriction from the rest of the body, en face view showing no clear separation between subdorsal, subventral and lateral sectors. Stylet relatively short and slender (13-14.5 μm) with round to slightly concave anteriorly oriented knobs. Pharyngeal glands overlap 10.9-34.7 μm long. Female reproductive system with oval to slightly rounded spermatheca without sperm except for one specimen with sperm. Tail subcylindrical to conoid with high variability of tail tip from rounded, truncate to indented. Based on morphology and morphometrics the new species is most closely related to P. oleae but also closely resembles P. delattrei, P. elamini, P. sudanensis, P. cruciferus, P. mediterraneus and P. microstylus. Phylogenetic analysis based on the D2-D3 expansion region of 28S rDNA, 18S rDNA and COI of mitochondrial DNA confirmed its status as a new species within a well-supported clade including P. oleae, P. convallariae, P. penetrans, P. brachyurus, P. arlington, P. dunensis, P. fallax and P. pinguicaudatus.