Genomic selection models can be trained using historical data and filtering genotypes based on phenotyping intensity and reliability criterion are able to increase the prediction ability. We implemented genomic selection based on a large commercial population incorporating 2325 European winter wheat lines. Our objectives were (1) to study whether modeling epistasis besides additive genetic effects results in enhancement on prediction ability of genomic selection, (2) to assess prediction ability when training population comprised historical or less-intensively phenotyped lines, and (3) to explore the prediction ability in subpopulations selected based on the reliability criterion. We found a 5 % increase in prediction ability when shifting from additive to additive plus epistatic effects models. In addition, only a marginal loss from 0.65 to 0.50 in accuracy was observed using the data collected from 1 year to predict genotypes of the following year, revealing that stable genomic selection models can be accurately calibrated to predict subsequent breeding stages. Moreover, prediction ability was maximized when the genotypes evaluated in a single location were excluded from the training set but subsequently decreased again when the phenotyping intensity was increased above two locations, suggesting that the update of the training population should be performed considering all the selected genotypes but excluding those evaluated in a single location. The genomic prediction ability was substantially higher in subpopulations selected based on the reliability criterion, indicating that phenotypic selection for highly reliable individuals could be directly replaced by applying genomic selection to them. We empirically conclude that there is a high potential to assist commercial wheat breeding programs employing genomic selection approaches.

In vivo haploid induction has become a routine tool for rapid line development in maize (Zea mays L.). However, distinguishing haploid (H) from diploid crossing (C) seeds is problematic for many germplasms due to poor expression or suppression of the currently‐used R1‐nj embryo marker. We examined a new approach for sorting H and C seeds on the basis of their oil content (OC). Ten source germplasms, including single crosses, synthetics, and landraces, were pollinated by high‐oil (HO) inducer UH600 with OC = 10.8%. Identification of embryoless seeds based on seed OC < 2.1% was very reliable. The average difference (1.79%) between the mean OC of C and H seeds was more than twice the standard deviation (SD) within each fraction. Thus, sorting H and C seeds based on OC smaller or greater than an a priori chosen threshold t was generally more reliable than based on the R1‐nj embryo marker. Another ten source germplasms were pollinated with normal‐oil inducer UH400 with OC = 3.0%. Since the difference (0.65%) between OC of C and H seeds was approximately of the same magnitude as the SD, both fractions overlapped too much for reliable sorting. The discrimination of H and C seeds based on their OC looks very promising, even for heterogeneous source materials such as landraces, provided an HO inducer and a stringent threshold t are used. In combination with high‐throughput platforms for automated sorting of single seeds for OC, this opens new avenues for extending the application and increasing the efficiency of the double haploid technology in maize.

In vivo production of doubled‐haploid (DH) lines in maize (Zea mays L.) routinely involves artificial chromosome doubling by colchicine treatment of seedlings. Because colchicine is a hazardous chemical, replacing it by less‐toxic alternatives would be highly desirable. Our objectives were to (i) test the efficacy of various herbicides alone or in combination with other herbicides or phytohormones as chromosome doubling agents, (ii) evaluate the efficacy of application of these chemicals for different durations and methods of delivery to meristems, and (iii) compare colchicine treatment with the most promising alternative treatment under economic aspects. Several antimitotic herbicides with different modes of action and two phytohormones were tested in various combinations and concentrations in four experiments for survival rate (SR) of germinated seedlings, reproduction rate (RR) measured as the proportion of D0 plants with seed set, and overall success rate (OSR) measured as the proportion of D1 ears with seed set obtained from the germinated seedlings. Amiprophos‐methyl (APM) and pronamid, applied with the seedling soaking method, outperformed all other alternative treatments tested and reached almost the same OSR as colchicine. Cost comparison between the best treatment, containing APM and pronamid, and the colchicine control showed that the total production cost per D0 plant with seed set was about 10% higher than for colchicine as a result of slightly lower OSR. In conclusion, APM combined in an optimum dosage with pronamid is a promising alternative to colchicine in view of the lower toxicity and similar rate of chromosome doubling in maize.

The genetics underlying heterosis, the difference in performance of crosses compared with midparents, is hypothesized to vary with relatedness between parents. We established a unique germplasm comprising three hybrid wheat sets differing in the degree of divergence between parents and devised a genetic distance measure giving weight to heterotic loci. Heterosis increased steadily with heterotic genetic distance for all 1903 hybrids. Midparent heterosis, however, was significantly lower in the hybrids including crosses between elite and exotic lines than in crosses among elite lines. The analysis of the genetic architecture of heterosis revealed this to be caused by a higher portion of negative dominance and dominance-by-dominance epistatic effects. Collectively, these results expand our understanding of heterosis in crops, an important pillar toward global food security.

Fusarium head blight and Septoria tritici blotch resistances are complex traits and can be improved efficiently by genomic selection modeling main and epistatic effects. Enhancing the resistance against Fusarium head blight (FHB) and Septoria tritici blotch (STB) is of central importance for a sustainable wheat production. Our study is based on a large experimental data set of 2325 inbred lines genotyped with 12,642 SNP markers and phenotyped in multi-environmental trials for FHB and STB resistance as well as for plant height. Our objectives were to (1) investigate the impact of plant height on FHB and STB severity, (2) examine the potential of marker-assisted selection, and (3) study the prediction ability of genomic selection modeling main and epistatic effects. We observed low correlations between plant height and FHB (r = -0.15; P < 0.05) as well as STB severity (r = -0.17; P < 0.05) suggesting negligible morphological resistances. Cross-validation in combination with association mapping revealed absence of large effect QTL impeding an efficient pyramiding of different resistance loci through marker-assisted selection. The prediction ability of genomic selection was high amounting to 0.6 for FHB and 0.5 for STB resistance. Therefore, genomic selection is a promising tool to improve FHB and STB resistance in wheat.

Ergot caused by Claviceps purpurea (Fr.) Tul. is a serious threat to rye (Secale cereale L.) cultivation. It produces sclerotia containing a mixture of alkaloids toxic to animals and humans. For improving ergot resistance in rye a reliable field testing with a minimal disturbance by pollen transfer between plots is indispensable. We evaluated 85 rye cultivars of four types of cultivar (population, synthetic, and hybrid cultivars, hybrids blended with 10% population rye) under inoculation in 3 years (2005, 2006 and 2007) and analysed ergot incidence (% of affected heads) and ergot severity (% of sclerotia in grain by weight) at nine and ten environments (location · year combinations), respectively. Cultivar types were separated by border plots and each entry was additionally surrounded by four border plots of similar size (3-8 m 2 ) in a chess-board design. Disease level ranged from 10-27% affected heads and 0.7-2.6% sclerotia in grain in individual environments. Both, cultivar type and cultivars showed significant (P = 0.01) variation for both traits, interactions with environment were also significant (P = 0.01). Population cultivars had less than half the disease level than the other types of cultivar for both traits. Synthetic, hybrid, and blended hybrid cultivars did on average not differ significantly from each other. Blending had an ergot-reducing effect only for the more susceptible entries. The best two hybrid cultivars showed an ergot reaction similar to some population cultivars. However, the best population cultivar still had only half the amount of sclerotia in grain than the best hybrid cultivar (0.37% vs. 0.89%). Ergot incidence and ergot severity were highly (P = 0.01) correlated. We conclude that a good genotypic differentiation among rye cultivars is achievable by field inoculation of Claviceps purpurea across years with this design and testing within national listing trials is feasible.

A plethora of maize (Zea mays L.) landraces is stored in gene banks worldwide. However, information about their value in breeding is scarce and strategies for identifying the most promising landraces in prebreeding are largely lacking. This study was conducted to (i) evaluate the testcross performance of 70 European flint landraces in combination with two elite dent testers and compare these results with the performance of modern hybrids for important agronomic traits, (ii) estimate the genetic variances among landraces and trait correlations for these two testcross series as well as the correlation between them, and (iii) devise a testing scheme for assessing the breeding potential of a large number of landraces for hybrid breeding. Grain yield of the landrace testcrosses was on average about 26% lower than modern hybrids. Genotypic variances among landrace testcrosses were significant for all traits, and genetic correlations were moderate to high for most trait combinations in both testcross series. Thus, it seems promising to tap this huge genetic reserve for enlarging the genetic base of the elite flint germplasm pool in Central Europe. Since the genetic correlation between the two testcross series exceeded 0.74 for all traits, we recommend assessing the breeding potential of landraces for broadening existing heterotic groups by evaluating their testcross performance in combination with one or two elite single‐cross tester(s) from the opposite heterotic pool. Subsequently, doubled haploid lines from a few of the most promising landraces could be produced to exploit the large genetic variation within landraces to the full extent.

Rapid production of inbred lines by in vivo haploid induction has become a routine method in maize breeding. Limitations of the present method can be overcome by use of inducers with high seed‐oil content for discrimination of haploid (H) from diploid crossing (C) seeds. With regard to the optimum application of this new approach, our goal was to find the most accurate discrimination method comparing the directly measured parameters oil mass (OM) and seed weight (SW) with the derived parameter oil content (OC). For this, we compared the distribution properties of H and C seeds from 11 induction crosses with high‐oil inducers for all three traits. The distributions of H and C seeds overlapped almost completely for SW but overlapped less for OC than for OM owing to a much smaller coefficient of variation in both fractions. Thus, the false discovery rate and false negative rate for sorting of H and C seeds were generally smaller for OC than for OM. The optimal bivariate discrimination function on the basis of OM and SW yielded similar error rates as a univariate discrimination function on the basis of OC alone. In conclusion, we recommend to measure seeds from induction crosses produced with high‐oil inducers for SW in addition to OM and use OC as a simple and robust criterion for sorting of H and C seeds.