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.).

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.

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The adaptability of wheat varieties to precise environmental conditions is known to be influenced to a large extent by photoperiod sensitive genes determining ear emergence time and by the gibberelic acid insensitive dwarfing genes that are regularly used to reduce plant height. A range of European winter wheat varieties were examined to establish whether breeders in different countries have selected genotypes carrying allelic variants of photoperiodic and dwarfing genes that would be expected to provide the best levels of adaptability. In most areas modern cultivars were seen to carry the genotypes predicted to promote good levels of adaptability. Varieties cultivated in Germany however are still predominately of conventional height and late flowering lacking genes that would be expected to enhance adaptability and yield.

Differences in development among wheat cultivars are not only restricted to photoperiod and vernalization responses. When both requirements are fully satisfied differences may still arise due to earliness per se. It is not clear at present to what extent this trait is ‘intrinsically’ expressed (a constitutive trait) independently of the environmental conditions so that it might be selected under any thermal condition or if it may be altered to the extent of showing a crossover interaction with temperature in which the ranking of wheat genotypes may be altered. The present study assessed the influence of temperature on the intrinsic earliness for lines of diploid wheat characterized for their differences in a major gene for intrinsic earliness, but also possibly differing in their genetic background for other factors controlling this polygenic trait. To do so the lines were grown individually in two temperature regimes (16 and 23°C) under long days having previously been fully vernalized. Multiple comparisons analyses were carried out among lines of the same allelic group for the Eps-Am1 gene. Results indicated that within each group there were lines that did not differ in their earliness per se, others differed but without exhibiting any line×temperature interaction and finally different types of interaction were shown, including cases where the ranking of lines was altered depending on the growing temperature. It is thus possible that the selection of a genotype based on its earliness per se in an environment might not represent the same performance in another location where temperature varied significantly.

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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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