Soft rot caused by Pectobacterium carotovorum (Pc) is a devastating disease of Brassica rapa, causing substantial reductions in crop yield and quality.  Identifying genes related to soft rot resistance is the key to solving this problem.  To characterize soft rot resistance, we screened a soft rot-susceptible Chinese cabbage (A03), a resistant pakchoi (‘Huaguan’), and a resistant mutant (sr).  An F₂ population was generated by crossing susceptible Chinese cabbage A03 and resistant pakchoi ‘Huaguan’ to identify quantitative trait loci (QTLs) that confer soft rot resistance.  A high-density genetic map was constructed and the three QTLs identified contain 166 genes.  Based on available transcriptome data, we analyzed the expression of the 166 genes during an important defense regulatory period in Pc infection in both A03 and the resistant mutant sr.  Among the 166 genes, six candidate genes were related to the soft rot defense response in B. rapa.  TIFY10B (JAZ2, BraA07g038660.3C) was located in the major soft rot resistance QTL, DRQTL-3 on A07, and we speculate that this gene may play an important role in the defense mechanism against soft rot in B. rapa.  This study lays the foundation for further investigations on the mechanism of soft rot resistance in B. rapa crops.

MicroRNAs (miRNAs), which post-transcriptionally regulate gene expression by binding to the 3´ untranslated region of mRNAs to either inhibit or enhance translation, are involved in diverse biological processes. The use of high-throughput Solexa sequencing plays important roles in the discovery of miRNAs. In this study, we used high-throughput Solexa sequencing to identify novel duck miRNAs and compare the miRNA expression profiles in laying and non-laying duck ovaries. Using a bioinformatic analysis, we discovered 86 potential duck miRNAs similar to known chicken miRNAs and 43 unique sequences that matched known miRNAs of other species. We also found that miRNA variations and isoforms were widespread in our two RNA libraries, with most of the variations occurring in the 3´ region of the miRNAs. Furthermore, we detected 55 miRNAs that exhibited significant expression differences between laying and non-laying ducks. Gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses of the potential targets of the differentially expressed miRNAs indicated these miRNAs may play key roles in the egg laying process. Finally, we confirmed the differential expression of 5 miRNAs in the laying and non-laying samples by qRT-PCR. Cumulatively, our work provides the first look at the miRNA expression profile of the duck ovary and provides novel insight into the roles of miRNAs in egg laying and reproduction.