Author(s):
Figueiredo, Joana 
; Simões, Maria José ; Gomes, Paula ; Barroso, Cristina ; Pinho, Diogo ; da Conceição, I. L. P. M. ; Fonseca, Luís ; Abrantes, I. M. O. ; Pinheiro, Miguel ; Egas, Conceição
Date: 2013
Persistent ID: http://hdl.handle.net/10316/25575
Origin: Estudo Geral - Universidade de Coimbra
Description
The pinewood nematode, Bursaphelenchus xylophilus, is native to North America but it only causes damaging pine wilt
disease in those regions of the world where it has been introduced. The accurate detection of the species and its dispersal
routes are thus essential to define effective control measures. The main goals of this study were to analyse the genetic
diversity among B. xylophilus isolates from different geographic locations and identify single nucleotide polymorphism
(SNPs) markers for geographic origin, through a comparative transcriptomic approach. The transcriptomes of seven B.
xylophilus isolates, from Continental Portugal (4), China (1), Japan (1) and USA (1), were sequenced in the next generation
platform Roche 454. Analysis of effector gene transcripts revealed inter-isolate nucleotide diversity that was validated by
Sanger sequencing in the genomic DNA of the seven isolates and eight additional isolates from different geographic
locations: Madeira Island (2), China (1), USA (1), Japan (2) and South Korea (2). The analysis identified 136 polymorphic
positions in 10 effector transcripts. Pairwise comparison of the 136 SNPs through Neighbor-Joining and the Maximum
Likelihood methods and 5-mer frequency analysis with the alignment-independent bilinear multivariate modelling
approach correlated the SNPs with the isolates geographic origin. Furthermore, the SNP analysis indicated a closer proximity
of the Portuguese isolates to the Korean and Chinese isolates than to the Japanese or American isolates. Each geographic
cluster carried exclusive alleles that can be used as SNP markers for B. xylophilus isolate identification.
