Introgression of Thinopyrum elongatum DNA fragments carrying resistance to fusarium head blight into Triticum aestivum cultivar Chinese Spring is associated with alteration of gene expression.

The tall wheatgrass species Thinopyrum elongatum carries on the long arm of its chromosome 7E a locus contributing strongly to resistance to fusarium head blight (FHB), a devastating fungal disease affecting wheat crops in all temperate areas of the world. Introgression of Th. elongatum 7E chromatin into chromosome 7D of wheat was induced by the ph1b mutant of CS. Recombinants between chromosome 7E and wheat chromosome 7D, induced by the ph1b mutation, were monitored by a combination of molecular markers and phenotyping for FHB resistance. Progeny of up to five subsequent generations derived from two lineages, 64-8 and 32-5, were phenotyped for FHB symptoms and genotyped using published and novel 7D- and 7E-specific markers. Fragments from the distal end of 7EL, still carrying FHB resistance and estimated to be less than 114 and 66 Mbp, were identified as introgressed into wheat chromosome arm 7DL of progeny derived from 64-8 and 32-5, respectively. Gene expression analysis revealed variation in the level of expression of genes from the distal ends of 7EL and 7DL in the introgressed progeny. The 7EL introgressed material will facilitate use of the 7EL FHB resistance locus in wheat breeding programs.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Development and validation of –expressed molecular markers specific for the long arm of Chromosome 7E

The ditelocentric addition line CS-7EL of the spring wheat (Triticum aestivum L.) cultivar Chinese Spring (CS) contains the long arm of the chromosome 7E from Thinopyrum elongatum (CS-7EL), which confers high resistance to Fusarium head blight. It is of great interest to breeders to integrate the resistance locus (loci) from Th. elongatum into commercial wheat varieties. The objectives of this study were to identify candidate genes expressed from the 7EL chromosome of CS-7EL, to develop 7EL-specific molecular markers, and to validate their usefulness for characterizing recombination between one of the group 7 chromosomes of wheat and Th. elongatum. High-throughput sequencing of Fusarium graminearum–infected and control CS and CS-7EL cDNA libraries was performed using RNA-Seq. A stepwise bioinformatics strategy was applied to assemble the sequences obtained from RNA-Seq and to create a conservative list of candidate genes expressed from the foreign chromosome 7EL. Polymerase chain reaction primer pairs were designed and tested for 135 candidate genes. A total of 48 expressed molecular markers specific for the chromosome 7EL were successfully developed. Screening of progenies from two BC1F2 families from the cross CS-7E(7D) × 2*CSph1b showed that these markers are useful for characterizing recombination events between the chromosomes 7D from wheat and 7E from Th. elongatum

Comparative Transcriptome Profiles of Near-Isogenic Hexaploid Wheat Lines Differing for Effective Alleles at the 2DL FHB Resistance QTL

Fusarium head blight (FHB), caused by the fungus Fusarium graminearum, represents one of the major wheat diseases worldwide, determining severe yield losses and reduction of grain quality due to the accumulation of mycotoxins. The molecular response associated with the wheat 2DL FHB resistance QTL was mined through a comprehensive transcriptomic analysis of the early response to F. graminearum infection, at 3 days post-inoculation, in spikelets and rachis. The analyses were conducted on two near isogenic lines (NILs) differing for the presence of the 2DL QTL (2-2618, resistant 2DL+ and 2-2890, susceptible null). The general response to fungal infection in terms of mRNAs accumulation trend was similar in both NILs, even though involving an higher number of DEGs in the susceptible NIL, and included down-regulation of the primary and energy metabolism, up-regulation of enzymes implicated in lignin and phenylpropanoid biosynthesis, activation of hormons biosynthesis and signal transduction pathways and genes involved in redox homeostasis and transcriptional regulation. The search for candidate genes with expression profiles associated with the 2DL QTL for FHB resistance led to the discovery of processes differentially modulated in the R and S NILs related to cell wall metabolism, sugar and JA signaling, signal reception and transduction, regulation of the redox status and transcription factors. Wheat FHB response-related miRNAs differentially regulated were also identified as putatively implicated in the superoxide dismutase activities and affecting genes regulating responses to biotic/abiotic stresses and auxin signaling. Altered gene expression was also observed for fungal non-codingRNAs. The putative targets of two of these were represented by the wheat gene WIR1A, involved in resistance response, and a gene encoding a jacalin-related lectin protein, which participate in biotic and abiotic stress response, supporting the presence of a cross-talk between the plant and the fungus