ABSTRACT: Powdery mildew caused by Erysiphe cruciferarum, is an epidemic of oil rapeseed (Brassica napus) growing worldwide, but resistant germplasm is rare in this species. We obtained the hybrid seeds of distant hybridization between powdery-mildew-immune Brassica carinata cultivar ‘White flower’ and susceptible B. napus cultivar ‘Zhongshuang11’. Five lines in the BC1F3 generation (F3 after backcross to 'Zhongshuang11') were identified to be resistant or moderately resistant. In order to identify the important biological responses to powdery mildew, the foliar transcriptomes of the resistant and susceptible plants in these progenies after powdery mildew inoculation were compared by using Illumina RNA-seq. We identified 10,454 differential expression genes (DEGs) and 1050 genes out of them are related to disease resistance. There were 271 DEGs in Group Resistance expressed at least two fold higher than in group S, while 779 DGEs expressed two fold lower. The genes highly expressed in Group Resistance are those encoding the proteins: (1) related to wax, chloroplast and cell wall metabolism, such as KCS6, CSP41B, RWA, callose synthetase 3, pectinase 9, fructosidase 2, 9s-lipoxygenase LOX2, etc.; (2) kinases including RKL, ERECTA, BAK1, BAM2, LysM receptor like kinase, and lipid transfer protein kinase ERl1 and ERl2; (3) broad spectrum powdery mildew resistance proteins RPW8, calmodulin MLO2, PMR5, MLP328, EDR2, RPS4 and RPS6, etc. In group susceptible, pectinesterase, cytochrome CYP81f2, LOX1, cysteine rich receptor protein kinases and serine / threonine protein kinases such as MEKK, RLK6, CRK45, APK1, BRl3, WAK1, WAK10, etc., and TIR-NB-LRR receptor like proteins R1M1, DSC1, DSC2 and pathogenesis-related protein PR-1 etc. were the most activated genes. The results provide the preliminarily knowledge about molecular mechanism in rapeseed defense response to powdery mildew.
