QTL Mapping Combined with Microarray Profiling Data for the Identification of Pine Wood Nematode (PWN) Resistance Genes in Pinus thunbergii

Pine wilt disease is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus, and is a chronic problem to pine forests (Pinus thunbergii and Pinus densiflora) in Japan. We combined microarray profiling and QTL mapping to identify QTL genes for Pine wood nematode (PWN) resistance in Pinus thunbergii. Two clones, Tosashimizu63 and Takahagi1, which are resistant and susceptible cultivars, respectively, to the isolate Ka4 infection were utilized in microarray profiling. We constructed pairwise comparisons followed by fold change analysis using time-course sampling of trees inoculated with PWN at 1, 3, or 7 days post-inoculation (dpi). The expression levels of 357 transcripts changed significantly between resistant and susceptible cultivars, and which used to SNP genotyping in segregating F(1) population (resistant × susceptible) using the Fluidigm EP1 system. Additionally, a previously developed 150 genomic SSR marker were used to construct frame of genetic map. By performing QTL mapping using 192 F(1) of the resistant and susceptible cultivars for the PWN resistance, we identified one major locus.