Earliness per se genes are those that regulate flowering time independently of vernalization and photoperiod, and are important for the fine tuning of flowering time and for the wide adaptation of wheat to different environments. The earliness per se locus Eps-Am1 was recently mapped within a 0.8 cM interval on chromosome 1AmL of diploid wheat Triticum monococcum L., and it was shown that its effect was modulated by temperature. In this study, this precise mapping information was used to characterize the effect of the Eps-Am1 region on both duration of different developmental phases and spikelet number. Near isogenic lines (NILs) carrying the Eps-Am1-l allele from the cultivated accession DV92 had significantly longer vegetative and spike development phases (P <0.0001) than NILs carrying the Eps-Am1-e allele from the wild accession G3116. These differences were paralleled by a significant increase in the number of spikelets per spike, in both greenhouse and field experiments (P <0.0001). Significant interactions between temperature and Eps-Am1 alleles were detected for heading time (P <0.0001) but not for spikelet number (P=0.67). Experiments using NILs homozygous for chromosomes with recombination events within the 0.8 cM Eps-Am1 region showed that the differences in number of spikelets per spike were linked to the differences in heading time controlled by the Eps-Am1 locus. These results indicate that the differences in these two traits are either pleiotropic effects of a single gene or the effect of closely linked genes. A similar effect on spikelet number was detected in the distal region of chromosome 1AL in common wheat (T. aestivum L.).

Wheat cultivars exposed to optimal photoperiod and vernalization treatments still exhibit differences in flowering time, referred to as earliness per se (Eps). We previously identified the Eps-Am1 locus from Triticum monococcum and showed that the allele from cultivated accession DV92 significantly delays heading time and increases the number of spikelets per spike relative to the allele from wild accession G3116. Here, we expanded a high-density genetic and physical map of the Eps-Am1 region and identified the wheat ortholog of circadian clock regulator EARLY FLOWERING 3 (ELF3) as a candidate gene. No differences in ELF3 transcript levels were found between near-isogenic lines carrying the DV92 and G3116 Eps-Am1 alleles, but the encoded ELF3 proteins differed in four amino acids. These differences were associated with altered transcription profiles of PIF-like, PPD1, and FT1, which are known downstream targets of ELF3. Tetraploid wheat lines with combined truncation mutations in the A- and B-genome copies of ELF3 flowered earlier and had less spikelets per spike than the wild-type control under short- and long-day conditions. Both effects were stronger in a photoperiod-sensitive than in a reduced photoperiod-sensitive background, indicating a significant epistatic interaction between PPD1 and ELF3 (P < 0.0001). By contrast, the introgression of the T. monococcum chromosome segment carrying the Eps-Am1 allele from DV92 into durum wheat delayed flowering and increased the number of spikelets per spike. Taken together, the above results support the hypothesis that ELF3 is Eps-Am1. The ELF3 alleles identified here provide additional tools to modulate reproductive development in wheat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10142-016-0490-3) contains supplementary material, which is available to authorized users.

An earliness per se gene, designated Eps-A m 1, was mapped in diploid wheat in F 2 and single-seed descent mapping populations from the cross between cultivated (DV92) and wild (G3116) Triticum monococcum accessions. A QTL with a peak on RFLP loci Xcdo393 and Xwg241, the most distal markers on the long arm of chromosome 1A m , explained 47% of the variation in heading date (LOD score 8.3). Progeny tests for the two F 2:3 families with critical recombination events between Xcdo393 and Xwg241 showed that the gene was distal to Xcdo393 and linked to Xwg241. Progeny tests and replicated experiments with line #3 suggested that Eps-A m 1 was distal to Xwg241. This gene showed a large effect on heading date in the controlled environment experiments, and a smaller, but significant, effect under natural conditions. Eps-A m 1 showed significant epistatic interactions with photoperiod and vernalization treatments, suggesting that the different classes of genes affecting heading date interact as part of a complex network that controls the timing of flowering induction. Besides its interactions with other genes affecting heading date, Eps-A m 1 showed a significant interaction with temperature. The effect of temperature was larger in plants carrying the DV92 allele for late flowering than in those carrying the G3116 allele for early flowering. Average differences in heading date between the experiments performed at 16°C and 23°C were approximately 11 days (P < 0.001) for the lines carrying the Eps-A m 1 allele for early flowering but approximately 50 days (P < 0.0001) for the lines carrying the allele for late flowering. The large differences in heading time (average 80 days) observed between plants carrying the G3116 and DV92 alleles when grown at 16°C, suggest that it would be possible to produce very detailed maps for this gene to facilitate its future positional cloning.

Wheat grain protein content (GPC) is important for human nutrition and has a strong influence on the quality of pasta and bread. The objective of this study was to analyse the introduction of the Gpc-B1 allele into two Argentinean bread wheat cultivars. Near-isogenic lines were developed in 'ProINTA Oasis' and 'ProINTA Granar' using marker-assisted selection. Gpc-B1 lines showed a significant (P = 0.01) increase in GPC and a significant (P = 0.001) decrease in grain weight in comparison with control lines without Gpc-B1. Differences in yield were not significant (P = 0.49) between lines. Gpc-B1 lines significantly reduced (P = 0.02) straw nitrogen concentration at maturity and significantly increased (P = 0.02) the nitrogen harvest index. When data were analysed by genotype and environment, differences in some analysed parameters were found, indicating that Gpc-B1 expression may be affected by different genetic backgrounds and environmental conditions. These results suggest that the introgression of the Gpc-B1 allele into Argentinean wheat germplasm could be a valuable resource for improving GPC with no detrimental effect on grain yield.

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The repeat units of the 18S–5.8S–26S ribosomal genes (rDNA) of 15 South American and 6 Asiatic and North American species of Elymus were shown to vary between 8.7 and 11.3 kb among species. Interspecific variation in the EcoRI and BamHI cleavage sites was observed. BamHI restriction sites were present in the subrepeats in the intergenic spacers in rDNA from diploid Hordeum (H genome) and absent in the diploid Pseudoroegneria (S genome) and in nearly all the tetraploid species of Elymus (SH genomes). Tetraploid Elymus species have only two pairs of chromosomes with secondary constrictions similar to those found in Pseudoroegneria and a maximum of two different repeat unit length classes. These results suggest that the rDNA in the H genome was lost during the evolution of the tetraploid Elymus. However, the additional H genome present in the hexaploid Elymus with genome formula SSHHH′H′ still show active ribosomal genes. Nucleolar organizer activity was also observed in rDNA from both the S and H genomes in artificial SS × HH amphiploids, suggesting no complete nucleolar dominance (amphiplasty) between the S and H genomes.Key words: Elymus, ribosomal genes, RFLP, nucleolus.

Fusarium head blight (FHB) is a fungal wheat (Triticum aestivum L.) disease associated with yield and quality losses and mycotoxin grain contamination. Host plant resistance is the most economical and efficient way of control. However, novel sources of resistance are required. The objectives of this study were to identify quantitative trait loci (QTL) for type II resistance against FHB in the spring wheat cultivar Catbird, released by CIMMYT, and to find low cost molecular markers linked to these QTL. A population of 102 doubled haploid lines derived from the cross between Catbird and Milan (a FHB‐susceptible cultivar) was genotyped with 209 microsatellite markers and assessed by single floret inoculation in a greenhouse during 2007, 2008, and 2011. One significant QTL, named QFhs.inta‐7D, was detected on chromosome 7DS. Additionally, two minor and unstable QTL were also detected on chromosomes 3BS and 5DL. Favorable alleles for all three QTL were derived from Catbird. QFhs.inta‐7D peaked at simple sequence repeat (SSR) marker cfd14, flanked by markers barc128 and wmc702, and explained, on average, 20% of the phenotypic variation. The chromosomal region associated with FHB resistance in this work represents an interesting source of type II resistance and adds diversity to the FHB resistance gene pool. Stacking QFhs.inta‐7D with other QTL may achieve more acceptable levels of FHB resistance in new commercial cultivars. Once validated, markers linked to QFhs.inta‐7D could be used in marker‐assisted selection programs.

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