An ancestral NB-LRR with duplicated 3'UTRs confers stripe rust resistance in wheat and barley.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a global threat to wheat production. Aegilops tauschii, one of the wheat progenitors, carries the YrAS2388 locus for resistance to Pst on chromosome 4DS. We reveal that YrAS2388 encodes a typical nucleotide oligomerization domain-like receptor (NLR). The Pst-resistant allele YrAS2388R has duplicated 3' untranslated regions and is characterized by alternative splicing in the nucleotide-binding domain. Mutation of the YrAS2388R allele disrupts its resistance to Pst in synthetic hexaploid wheat; transgenic plants with YrAS2388R show resistance to eleven Pst races in common wheat and one race of P. striiformis f. sp. hordei in barley. The YrAS2388R allele occurs only in Ae. tauschii and the Ae. tauschii-derived synthetic wheat; it is absent in 100% (n = 461) of common wheat lines tested. The cloning of YrAS2388R will facilitate breeding for stripe rust resistance in wheat and other Triticeae species

FLOWERING LOCUS T2 regulates spike development and fertility in temperate cereals

FLOWERING LOCUS T2 (FT2) is the closest paralog of the FT1 flowering gene in the temperate grasses. Here we show that overexpression of FT2 in Brachypodium distachyon and barley results in precocious flowering and reduced spikelet number, while down-regulation by RNA interference results in delayed flowering and a reduced percentage of filled florets. Similarly, truncation mutations of FT2 homeologs in tetraploid wheat delayed flowering (2-4 d) and reduced fertility. The wheat ft2 mutants also showed a significant increase in the number of spikelets per spike, with a longer spike development period potentially contributing to the delayed heading time. In the wheat leaves, FT2 was expressed later than FT1, suggesting a relatively smaller role for FT2 in the initiation of the reproductive phase. FT2 transcripts were detected in the shoot apical meristem and increased during early spike development. Transversal sections of the developing spike showed the highest FT2 transcript levels in the distal part, where new spikelets are formed. Our results suggest that, in wheat, FT2 plays an important role in spike development and fertility and a limited role in the timing of the transition between the vegetative and reproductive shoot apical meristem

Fine mapping of barley locus Rps6 conferring resistance to wheat stripe rust

[EN] Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major disease of wheat that is causing large economic losses in many wheat-growing regions of the world. Deployment of Pst resistance genes has been an effective strategy for controlling this pathogen, but many of these genes have been defeated by new Pst races. In contrast, genes providing resistance to this wheat pathogen in other grass species (nonhost resistance) have been more durable. Barley varieties (Hordeum vulgare ssp. vulgare) are predominately immune to wheat Pst, but we identified three accessions of wild barley (Hordeum vulgare ssp. spontaneum) that are susceptible to Pst. Using these accessions, we mapped a barley locus conferring resistance to Pst on the distal region of chromosome arm 7HL and designated it as Rps6. The detection of the same locus in the cultivated barley ‘Tamalpais’ and in the Chinese barley ‘Y12’ by an allelism test suggests that Rps6 may be a frequent component of barley intermediate host resistance to Pst. Using a high-density mapping population (>10,000 gametes) we precisely mapped Rps6 within a 0.14 cM region (~500 kb contig) that is colinear to regions in Brachypodium (<94 kb) and rice (<9 kb). Since no strong candidate gene was identified in these colinear regions, a dedicated positional cloning effort in barley will be required to identify Rps6. The identification of this and other barley genes conferring resistance to Pst can contribute to our understanding of the mechanisms for durable resistance against this devastating wheat pathogenSIDr. Fu acknowledges support from the National Natural Science Foundation of China (31110103917), the National Basic Research Program of China (2013CB127700 and 2011CB100700), the Tai’shan Scholar Program of Shandong Province, China, and the Cooperative Innovation Center of Efficient Production with High Annual Yield of Wheat and Corn, Shandong Province, China. Dr. Dubcovsky acknowledges support from the NRI grant 2011-68002-30029 (TCAP) from the USDA National Institute of Food and Agriculture, by the Borlaug Global Rust Initiative, and by the Howard Hughes Medical Institute and the Gordon and Betty Moore Foundation Grant GBMF303

Wheat VIN3-like PHD finger genes are up-regulated by vernalization.

The term 'vernalization' describes the acceleration of the transition between the vegetative and reproductive stages after exposing plants to an extended period of low temperature. In Arabidopsis, vernalization promotes flowering by silencing the flowering repressor gene FLOWERING LOCUS C (FLC). Mitotically stable repression of FLC is the result of chromatin modifications mediated by the Vernalization-INsensitive 3 (VIN3) and VIN3-Like (VIL) proteins. In this study, we identified and characterized three VIL genes in diploid wheat (Triticum monococcum L.), named TmVIL1, TmVIL2, and TmVIL3. Similar to Arabidopsis VIN3, all three wheat VIL proteins carry three conserved domains including a plant homeodomain finger motif (PHD), a fibronectin type III domain (FNIII), and a VIN3 interacting domain (VID). Genetic mapping placed TmVIL1, TmVIL2, and TmVIL3 loci in the centromeric regions of chromosome 5, 6, and 1, respectively. The chromosome location of TmVIL1 is close to that of the vernalization gene VRN-D5, but more precise mapping information is required to validate this relationship. Transcription of the wheat VIL genes was up-regulated by vernalization, with a peak after 4-6 weeks of cold treatment. When transferred back to warm conditions, transcript levels of the wheat VIL genes returned to pre-vernalization levels. In addition, the transcript levels of wheat VIL genes are affected by photoperiod. This study indicates that wheat VIL genes have retained a similar structure and transcriptional regulation as their Arabidopsis VIN3/VIL homologues, suggesting that they might have retained some of their functions

Technology for Production of Wheat Doubled Haploid via Maize Pollen Induction—Updated Review

Chromosome elimination resulting in haploids is achieved by rapid loss of chromosomes from one parent during the zygote stage and is an important procedure to produce doubled haploid (DH) lines in plants. During crosses between an emasculated wheat (Triticum aestivum L.) and maize (Zea mays L.) as pollen donors, the complete loss of maize chromosomes results in wheat haploid embryos. Through embryo rescue and chromosome doubling processes, pure lines with stable traits can be quickly obtained. The technique is called the “Wheat × Maize System”. Although this technology is not new, it remains a practical approach to date. In order to optimize and improve this technology and to achieve its maximum potential in the winter wheat area of China, this paper reviews the previous and ongoing research and technical procedures for the production of wheat DH lines via the maize pollen induction and presents outlooks on DH research and its application in wheat breeding