Abstract
A population of Xiphinema chambersi from the root zone around live oak (Quercus virginiana Mill.) trees on Jekyll Island, GA, is described using both morphological and molecular tools and compared with descriptions of type specimens. Initially, because of a few morphological differences, this nematode was thought to represent an undescribed species. However, on further examination, the morphometrics of the nematodes from live oak tend to agree with most of the morphometrics in the original description and redescription of X. chambersi except for few minor differences in V% relative to body length, slightly shorter stylet length, different c value, and the number of caudal pores. We consider these differences to be part of the normal variation within this species and accordingly image this new population of X. chambersi and redescribe the species. The new population is characterized by having females with a body length of 2.1 to 2.5 mm; lip region slightly rounded and set off from head; total stylet length 170 to 193 µm; vulva at 20.4% to 21.8% of body length; a monodelphic, posterior reproductive system; elongate, conoid tail with a blunt terminus and four pairs of caudal pores, of which two pairs are subdorsal and two subventral. Sequence data from the D2-D3 region of the 28S rRNA molecule subjected to GenBank sequence comparison using BLAST showed that the sequence had 96% and 99% similarity with X. chambersi from Alabama and Florida, respectively. Phylogenetic relationships of X. chambersi with other xiphinematids based on analysis of this DNA fragment are presented. This finding represents a new location of X. chambersi in Georgia on live oak for this species.
Highlights
A population of Xiphinema chambersi from the root zone around live oak (Quercus virginiana Mill.) trees on Jekyll Island, GA, is described using both morphological and molecular tools and compared with descriptions of type specimens
This population of Xiphinema showed females with a body length of 2.1 to 2.5 mm; lip region slightly rounded and set off from head; total stylet length 170 to 193 mm; vulva quite anteriorly located at 20.4% to 21.8% of body length; a monodelphic, posterior reproductive system; elongate, conoid tail with a blunt terminus and four pairs of caudal pores, of which two pairs are subdorsal and two subventral. It resembled X. chambersi Thorne, 1939; Xiphinema monohysterum Brown, 1968; Xiphinema insigne Loos, 1949; and Xiphinema mali Ganguly et al, 2002. These facts led us to undertake a detailed morphological and molecular comparative study with previously reported data combined with molecular analyses to help in its species identification and to clarify the phylogeny of some of the closely related species of the genus
These studies showed that the live oak population differed from all these Xiphinema species either in the body length, vulva position, stylet length, c and c9, or in the tail shape
Summary
Morphological characterization: Soil samples (2.5-cmdiam. to a 20-cm-depth) were collected from the root zone around live oak (Q. virginiana) trees on Jekyll Island, GA. Nematodes were extracted from a 200-cm composite soil sample that was thoroughly but gently mixed, using the technique of Flegg (1967) with modifications by Fraedrich and Cram (2002). Protocols for DNA extraction, PCR, and sequencing were described by Tanha Maafi et al (2003). Several clones of each sample were isolated using blue/white selection and submitted to PCR with same primers. PCR products from each clone were sequenced. Sequence of the ITS1 rRNA gene was aligned with those of other X. chambersi (Ye et al, 2004; Yu et al, 2010; Zeng et al, 2015) and two species outgroup species. BI analysis for each aligned dataset was initiated with a random starting tree and was run with four chains for 1.0 3 106 generations.
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