Oilseed rape (Brassica napus L.) was formed~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent A n and C n subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement.T he Brassicaceae are a large eudicot family (1) and include the model plant Arabidopsis thaliana. Brassicas have a propensity for genome duplications ( Fig. 1) and genome mergers (2). They are major contributors to the human diet and were among the earliest cultigens (3).B. napus (genome A n A n C n C n ) was formed by recent allopolyploidy between ancestors of B. oleracea (Mediterranean cabbage, genome C o C o ) and B. rapa (Asian cabbage or turnip, genome A r A r ) and is polyphyletic (2, 4), with spontaneous formation regarded by Darwin as an example of unconscious selection (5). Cultivation began in Europe during the Middle Ages and spread worldwide. Diversifying selection gave rise to oilseed rape (canola), rutabaga, fodder rape, and kale morphotypes grown for oil, fodder, and food (4, 6).The homozygous B. napus genome of European winter oilseed cultivar 'Darmor-bzh' was assembled with long-read [>700 base pairs (bp)] 454 GS-FLX+ Titanium (Roche, Basel, Switzerland) and Sanger sequence (tables S1 to S5 and figs. S1 to S3) (7). Correction and gap filling used 79 Gb of Illumina (San Diego, CA) HiSeq sequence. A final assembly of 849.7 Mb was obtained with SOAP (8) and Newbler (Roche), with 89% nongapped sequence (tables S2 and S3). Unique mapping of 5× nonassembled 454 sequences from B. rapa ('Chiifu') or B. oleracea (' TO1000') assigned most of the 20,702 B. napus scaffolds to either the A n (8294) or the C n (9984) subgenomes (tables S4 and S5 and fig. S3). The assembly covers~79% of the 1130-Mb genome and includes 95.6% of Brassica expressed sequence tags (ESTs) (7). A single-nucleotide polymorphism (SNP) map (tables S6 to S9 and figs. S4 to S8) genetically anchored 712.3 Mb (84%) of the genome assembly, yielding pseudomolecules for the 19 chromosomes (table S10).The assembled C n subgenome (525.8 Mb) is larger than the A n subgenome (314.2 Mb), consistent with the relative sizes of the assembled C o genome of B. oleracea (540 Mb, 85% of thẽ 630-Mb genome) and the A r genome of B. rapa (312 Mb, 59% of the~530-Mb genome) (9-11). The B. napus assembly contains 34.8% transposable elements (TEs), less than the 40% estimated from raw reads (table...

Barley is a very important crop worldwide and has good impact in preserving food security. The impacts of 10 mM proline and 0.5 mM salicylic acid were evaluated on water stressed barley plants (Hordeum vulgare L. Giza126). Salicylic acid and proline treatments led to increased stem length, plant dry weights, chlorophyll concentration, relative water content, activity of antioxidant enzymes, and grain yield under drought stress. Nevertheless, lipid peroxidation, electrolyte leakage (EL), superoxide (O2·−), and hydrogen peroxide (H2O2) significantly decreased in treated barley plants with proline and salicylic acid in both growing seasons as compared with drought treatment only, which caused significant decrease in stem length, plant dry weights, chlorophyll concentration, activity of antioxidant enzymes, as well as biological and grain yield. These results demonstrated the importance of salicylic acid and proline as tolerance inducers of drought stress in barley plants.

Plant disease-resistance genes play a critical role in providing resistance against pathogens. The largest family of resistance genes are the nucleotide-binding site (NBS) and leucine-rich repeat (LRR) genes. They are classified into two major subfamilies, toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) and coiled-coil (CC)-NBS-LRR (CNL) proteins. We have identified and characterised 641 NBS-LRR genes in Brassica napus, 249 in B. rapa and 443 in B. oleracea. A ratio of 1 : 2 of CNL : TNL genes was found in the three species. Domain structure analysis revealed that 57% of the NBS-LRR genes are typical resistance genes and contain all three domains (TIR/CC, NBS, LRR), whereas the remaining genes are partially deleted or truncated. Of the NBS-LRR genes, 59% were found to be physically clustered, and individual genes involved in clusters were more polymorphic than those not clustered. Of the NBS-LRR genes in B. napus, 50% were identified as duplicates, reflecting a high level of genomic duplication and rearrangement. Comparative analysis between B. napus and its progenitor species indicated that >60% of NBS-LRR genes are conserved in B. napus. This study provides a valuable resource for the identification and characterisation of candidate NBS-LRR genes.