Field experiments in Europe have shown that Chinese cultivars of winter oilseed rape ( Brassica napus ) are very susceptible to the pathogen Leptosphaeria maculans (cause of phoma stem canker). Climatic and agronomic conditions in China are suitable for L. maculans since the closely related but less damaging pathogen L. biglobosa occurs on the winter and spring oilseed rape crops there. Major gene resistance to L. maculans is not durable; when introduced into commercial oilseed rape cultivars it is rapidly rendered ineffective by changes in the pathogen population. The threat to Chinese oilseed rape production from L. maculans is illustrated by the way in which L. maculans has spread into other areas of the world where previously only L. biglobosa was present, such as Canada and Poland. Models were developed to describe the spread (in space and time) of L. maculans across Alberta province, Canada, based on survey data collected over a 15-year period. These models were used to estimate the potential spread of L. maculans across the Yangtze river oilseed rape growing areas of China and its associated costs. Short-term strategies to prevent occurrence of severe phoma stem canker epidemics in China include training of extension workers to recognise symptoms of the disease and use of PCR-based diagnostics to detect the pathogen on imported seed. Long-term strategies include the introduction of durable resistance to L. maculans into Chinese oilseed rape cultivars as a component of an integrated disease management programme. The costs of such strategies in relation to costs of a phoma stem canker epidemic are discussed.

The Asian corn borer (ACB), Ostrinia furnacalis (Guenée), can develop strong resistance to Cry1Ab, the most widely commercialized Cry toxin for Bt maize worldwide. It is essential to understand the mechanism of resistance for management of this species, but information on the post-transcriptional regulation of Bt resistance in this target insect is limited. In the present study, RNA was extracted from the ACB in various larval stages (1–5 instar) from Cry1Ab-sensitive (ACB-BtS) and -resistant (ACB-AbR) strains, each of which included two biological replicates. Using Illumina sequencing, a total of 23,809,890 high-quality reads were collected from the four ACB libraries. The numbers of known microRNAs (miRNAs) were 302 and 395 for ACB-BtS and 268 and 287 for ACB-AbR. Using Mireap software, we identified 32 and 16 potential novel miRNAs for ACB-BtS and 18 and 22 for ACB-AbR. Among them, 21 known and 1 novel miRNAs had significantly different expression between ACB-BtS and ACB-AbR. Several miRNAs were observed to target potential Bt receptor genes, such as aminopeptidase N and cadherin-like protein. The glycosylphosphatidylinositol-anchor biosynthetic process and ABC transporters pathway were identified through Gene Ontology and KEGG pathway analysis of target genes of the differentially expressed miRNAs.

Summary Oligosaccharide, a typical danger‐associated molecular pattern (DAMP), has been studied and applied as plant defence elicitor for several years. Here, we report a novel oligosaccharide, mannan oligosaccharide (MOS) with a degree of polymerization of 2–6, which was hydrolysed from locust bean gum by a newly reported enzyme, BpMan5. The MOS treatment can significantly enhance the generation of signalling molecules such as intracellular Ca 2+ and reactive oxygen species. Subsequent defence events like stomata closure and cell death were also caused by MOS, eventually leading to the prevention of pathogen invasion or expansion. Transcriptional expression assay indicated that MOS activated mitogen‐activated protein kinase cascades in tobacco and rice via different cascading pathways. The expression levels of the defence‐related genes PR‐1a and LOX were both up‐regulated after MOS treatment, suggesting that MOS may simultaneously activate salicylic acid and jasmonic acid‐dependent signalling pathways. Furthermore, liquid chromatography‐mass spectrometry analysis showed that MOS led to the accumulation of four phytoalexins (momilactone A, phytocassane A, phytocassane D, and phytocassane E) in rice seedling leaves within 12–24 h. Finally, MOS conferred resistance in rice and tobacco against Xanthomonas oryzae and Phytophthora nicotianae , respectively. Taken together, our results indicated that MOS, a novel DAMP, could trigger multiple defence responses to prime plant resistance and has a great potential as plant defence elicitor for the management of plant disease.