BackgroundL. decemlineata is an exotic invasive insect pest, and invaded in Xinjiang Uygur autonomous region in China in the 1990s from Kazakhstan. It is a notorious defoliator of potato throughout most of the northern Xinjiang in current, and often causes extremely large yield losses of potato.ResultsThe expression stability of nine L. decemlineata house-keeping genes (Actin, ACT1 and ACT2; ADP-ribosylation factor, ARF1 and ARF4; TATA box binding protein, TBP1 and TBP2; ribosomal protein RP4 and RP18; translation elongation factor 1α EF1α) was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) in seven developmental stages, three larval tissues and two insecticide treatments. The results were analyzed using three software programs: geNorm, NormFinder and BestKeeper. Although there was no consistent ranking observed among the house-keeping genes across the samples, the overall analysis revealed that RP18, RP4, ARF1, and ARF4 were the four most stable house-keeping genes. In contrast, ACT1 and ACT2, two of the most widely used reference genes, had the least stability. Our results suggest that the combined use of the four most stably expressed genes may produce optimal normalization for qRT-PCR.ConclusionsThe expression stability of the house-keeping genes varies among different developing stages, in different tissues and under different experimental conditions. Our results will enable a more accurate and reliable normalization of qRT-PCR data in L. decemlineata.

Few quantitative trait loci (QTL) have been mapped for the expression of partial resistance to Phytophthora sojae in soybean and very little is known about the molecular mechanisms that contribute to this trait. Therefore, the objectives of this study were to identify additional QTL conferring resistance to P. sojae and to identify candidate genes that may contribute to this form of defense. QTL on chromosomes 12, 13, 14, 17, and 19, each explaining 4 to 7% of the phenotypic variation, were identifi ed using 186 RILs from a cross of the partially resistant cultivar 'Conrad' and susceptible cultivar 'Sloan' through composite interval mapping. Microarray analysis identifi ed genes with signifi cant differences in transcript abundances between Conrad and Sloan, both constitutively and following inoculation. Of these genes, 55 mapped to the fi ve QTL regions. Ten genes encoded proteins with unknown functions, while the others encode proteins related to defense or physiological traits. Seventeen genes within the genomic region that encompass the QTL were selected and their transcript abundance was confi rmed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). These results suggest a complex QTL-mediated resistance network. This study will contribute to soybean resistance breeding by providing additional QTL for marker-assisted selection as well as a list of candidate genes which may be manipulated to confer resistance.

SummaryAdaptation to climate across latitude and altitude reflects shared climatic constraints, which may lead to parallel adaptation. However, theory predicts that higher gene flow should favor more concentrated genomic architectures, which would lead to fewer locally maladapted recombinants.We used exome capture to resequence the gene space along a latitudinal and two altitudinal transects in the model tree Populus trichocapra. Adaptive trait phenotyping was coupled with F ST outlier tests and sliding window analysis to assess the degree of parallel adaptation as well as the genomic distribution of outlier loci.Up to 51% of outlier loci overlapped between transect pairs and up to 15% of these loci overlapped among all three transects. Genomic clustering of adaptive loci was more pronounced for altitudinal than latitudinal transects. In both altitudinal transects, there was a larger number of these 'islands of divergence', which were on average longer and included several of exceptional physical length.Our results suggest that recapitulation of genetic clines over latitude and altitude involves extensive parallelism, but that steep altitudinal clines generate islands of divergence. This suggests that physical proximity of genes in coadapted complexes may buffer against the movement of maladapted alleles from geographically proximal but climatically distinct populations.

Verticillium wilt of oilseed rape ( Brassica napus ) is caused primarily by Verticillium longisporum and has become a serious problem in northern Europe. In order to evaluate whether V. longisporum and V. dahliae differ in their interaction with oilseed rape, phenotypical and molecular assessments were made. Oilseed rape plants for fungal assessments were inoculated with V. longisporum and V. dahliae via root-dipping and samples were taken from roots, stems, leaves, flowers, pods and seeds during plant development. The infection by V. longisporum was found to start mainly in lateral roots and root-hairs, followed by colonization of the xylem vessels and extensive spread in stems and leaves, whereas V. dahliae infected the main roots and remained in the region below the cotyledon node of the plants. Re-isolation studies, together with PCR analysis of samples taken from early growth stages through to fully ripe plants, showed that the onset of flowering was a critical phase for V . longisporum to colonize plants. No seeds infected with V. longisporum were found. Mycelial growth from V. dahliae but not V. longisporum was significantly reduced on media containing tissue from a low glucosinolate B. napus genotype compared with growth on media containing tissue from a high glucosinolate cultivar. The results of this study suggest that V. longisporum favours B. napus as host and that the transition from the vegetative to the generative phase is of importance for the spread of the fungus in oilseed rape plants.

Extant variation in temperate and boreal plant species has been influenced by both demographic histories associated with Pleistocene glacial cycles and adaptation to local climate. We used sequence capture to investigate the role of these neutral and adaptive processes in shaping diversity in black cottonwood (Populus trichocarpa). Nucleotide diversity and Tajima's D were lowest at replacement sites and highest at intergenic sites, while LD showed the opposite pattern. With samples grouped into three populations arrayed latitudinally, effective population size was highest in the north, followed by south and centre, and LD was highest in the south followed by the north and centre, suggesting a possible northern glacial refuge. FST outlier analysis revealed that promoter, 5'-UTR and intronic sites were enriched for outliers compared with coding regions, while no outliers were found among intergenic sites. Codon usage bias was evident, and genes with synonymous outliers had 30% higher average expression compared with genes containing replacement outliers. These results suggest divergent selection related to regulation of gene expression is important to local adaptation in P. trichocarpa. Finally, within-population selective sweeps were much more pronounced in the central population than in putative northern and southern refugia, which may reflect the different demographic histories of the populations and concomitant effects on signatures of genetic hitchhiking from standing variation.