Rotylenchus wimbii n. sp. (Nematoda: Hoplolaimidae) associated with finger millet in Kenya

Rotylenchus wimbii n. sp. was found associated with finger millet in Kenya and is described based on light microscopy, scanning electron microscopy, and molecular information. Sequence analysis was performed on ITS, 18S, and D2-D3 of 28S of ribosomal DNA and COI of mitochondrial DNA. This new species is characterized by a moderate female body size of 0.6 to 0.8 mm, a continuous hemispherical lip region with four annuli, 3 to 4 irregular blocks on the basal lip annule, absence of longitudinal cuticular striations in anterior region, four lateral lines forming three equal bands which are areolated mainly at pharynx level, a robust stylet of 23 to 27 µm of which 45 to 53% is cone part, and with rounded to sometimes indented knobs, a secretory-excretory pore around level of pharyngo-intestinal junction, didelphic-amphidelphic reproductive system, vulva without distinct epiptygma, indistinct to empty spermatheca, tail usually truncated with 5 to 9 annuli, phasmids located at 7 to 17 annuli anterior to anus, and absence of males. Molecular phylogenies, in combination with species delimitation, supported the distinctiveness of Rotylenchus wimbii n. sp. and revealed some mislabeled Rotylenchus brevicaudatus sequences in GenBank.

Phylogenetic Analysis of the Hoplolaiminae Inferred from Combined D2 and D3 Expansion Segments of 28S rDNA

DNA sequences of the D2-D3 expansion segments of the 28S gene of ribosomal DNA from 23 taxa of the subfamily Hoplolaiminae were obtained and aligned to infer phylogenetic relationships. The D2 and D3 expansion regions are G-C rich (59.2%), with up to 20.7% genetic divergence between Scutellonema brachyurum and Hoplolaimus concaudajuvencus. Molecular phylogenetic analysis using maximum likelihood and maximum parsimony was conducted using the D2-D3 sequence data. Of 558 characters, 254 characters (45.5%) were variable and 198 characters (35.4%) were parsimony informative. All phylogenetic methods produced a similar topology with two distinct clades: One clade consists of all Hoplolaimus species while the other clade consists of the rest of the studied Hoplolaiminae genera. This result suggests that Hoplolaimus is monophyletic. Another clade consisted of Aorolaimus, Helicotylenchus, Rotylenchus, and Scutellonema species. Phylogenetic analysis using the outgroup species Globodera rostocheinsis suggests that Hoplolaiminae is paraphyletic. In this study, the D2-D3 region had levels of DNA sequence divergence sufficient for phylogenetic analysis and delimiting species of Hoplolaiminae.