Differentiation of the Xiphinema americanum-group nematodes X. brevicollum, X. incognitum, X. diffusum and X. oxycaudatum in Taiwan by morphometrics and nuclear ribosomal DNA sequences
Journal
Nematology
Journal Volume
7
Journal Issue
5
Pages
713-725
Date Issued
2005-07
Date
2005-07
Author(s)
Abstract
Morphometrics and molecular variability of the X. americanum-group collected in Taiwan were studied. Morphometric data, derived from the females and their developing juveniles, revealed that the 27 populations comprised four taxa: X. brevicollum, X. incognitum, X. diffusum and X. oxycaudatum, the last species being found to have only three juvenile stages. Further identifications were conducted by analysing the nucleotide sequences of the first internal transcribed spacer (ITS-1), 5.8S gene and second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA). Pairwise comparisons revealed the sequence differences among these taxa ranging from 3.5 to 21.8% for the ITS-1, 2.9 to 28.6% for the ITS-2 and 0 to 3.1% for the 5.8S. Little or no intraspecific variation was detected in the four species for which multiple populations from different geographical regions or hosts were sequenced. Although X. incognitum is morphometrically closer to X. diffusum than it is to X. brevicollum in mean body length, total stylet length, and percentage position of vulva, there is a higher degree of genetic similarity between X. incognitum and X. brevicollum.
Subjects
identification
Xiphinema americanum-group
ribosomal DNA
internal transcribed spacer
interspecific variation
intraspecific variation
juvenile stages
morphometrics
Publisher
Brill
Type
journal article