Quantitative trait loci (QTL) associated with resistance to Fusarium head blight (FHB), which is mainly caused by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schw. (Petch)], have been identified in wheat (Triticum aestivum L.) from different countries. Due to the differences of genetic backgrounds and analysis methods, the linked marker and significance levels of QTL are not consistent across studies. Such discrepancies make it difficult to select diagnostic flanking markers. Meta‐analysis has been used to estimate the confidence intervals (CIs) of QTL in plant and animal genomes. The objective of this study was to cluster 249 FHB resistance QTL identified in 46 unique lines from 45 studies based on the estimated QTL CI by meta‐analysis. A total of 209 QTL conditioning FHB resistance type I, II, III and IV were classified into 43 clusters on 21 chromosomes. Among them, 119 QTL were significant and 116 QTL explained more than 10% of phenotypic variation. There are 19 confirmed QTL located on chromosomes 3A, 5A, 7A, 1B, 3BS, 5B, 6B, and 2D. The results provide chromosome locations and linked markers for overlapping and unique QTL. Markers flanking QTL clusters can be used to pyramid diverse QTL more efficiently through marker‐assisted breeding.

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], also known as scab, is a destructive disease of wheat (Triticum aestivum L; T. turgidum L. var durum) and barley (Hordeum vulgare L.). Host resistance has long been considered the most practical and effective means of control, but breeding has been hindered by a lack of effective resistance genes and by the complexity of the resistance in identified sources. This paper will provide an overview of progress in developing host plant resistance for FHB, primarily in the USA, by review of the sources of resistance in wheat and barley, and their utilization in breeding programs. Although there are no reported sources of immunity, considerable genetic variability exists for resistance in both wheat and barley. Sources of resistance in durum, however, are limited. The strategy of breeding programs is to recombine different types and sources of resistance steadily through traditional breeding strategies. To facilitate selection, artificial inoculation techniques are used in both the field and greenhouse. This enables breeders to select simultaneously for resistance and desirable agronomic characteristics. Incremental increases in resistance are being reported in hexaploid wheat and to a lesser extent in barley and durum wheat. It is anticipated that the development of molecular markers will improve the efficiency of developing FHB wheat and barley cultivars.

Fusarium head blight (FHB), mainly caused by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schw. (Petch)], is an increasingly important disease of wheat (Triticum aestivum L.). Host-plant resistance provides the best hope for reducing economic losses associated with FHB, but new sources of resistance are limited. The moderately resistant winter wheat cultivar, Ernie, may provide a source of resistance that differs from Sumai 3 but these genes have not been mapped. Also hindering resistance breeding may be associations of resistance with agronomic traits such as late maturity that may be undesirable in some production environments. This research was conducted to identify QTL associated with type II FHB resistance (FHB severity, FHBS), and to determine if they are associated with days to anthesis (DTA), number of spikelets (NOS), and the presence/absence of awns. Two hundred and forty-three F(8) recombinant inbred lines from a cross between the resistant cultivar, Ernie and susceptible parent, MO 94-317 were phenotyped for type II FHB resistance using point inoculation in the greenhouse during 2002 and 2003. Genetic linkage maps were constructed using 94 simple sequence repeat (SSR) and 146 amplified fragment length polymorphic (AFLP) markers. Over years four QTL regions on chromosomes 2B, 3B, 4BL and 5A were consistently associated with FHB resistance. These QTL explained 43.3% of the phenotypic variation in FHBS. Major QTL conditioning DTA and NOS were identified on chromosome 2D. Neither the QTL associated with DTA and NOS nor the presence/absence of awns were associated with FHB resistance in Ernie. Our results suggest that the FHB resistance in Ernie appears to differ from that in Sumai 3, thus pyramiding the QTL in Ernie with those from Sumai 3 could result in enhanced levels of FHB resistance in wheat.

Based on the estimates of accuracy, genomic selection would be useful for selecting for improved trait values and trait stability for agronomic and quality traits in wheat. Trait values and trait stability estimated by two methods were generally independent indicating a breeder could select for both simultaneously. Genomic selection (GS) is a new marker-assisted selection tool for breeders to achieve higher genetic gain faster and cheaper. Breeders face challenges posed by genotype by environment interaction (GEI) pattern and selecting for trait stability. Obtaining trait stability is costly, as it requires data from multiple environments. There are few studies that evaluate the efficacy of GS for predicting trait stability. A soft winter wheat population of 273 lines was genotyped with 90 K single nucleotide polymorphism markers and phenotyped for four agronomic and seven quality traits. Additive main effect and multiplicative interaction (AMMI) model and  Eberhart and Russell regression (ERR) were used to estimate trait stability. Significant GEI variation was observed and stable lines were identified for all traits in this study. The accuracy of GS ranged from 0.33 to 0.67 for most traits and trait stability. Accuracy of trait stability was greater than trait itself for yield (0.44 using AMMI versus 0.33) and heading date (0.65 using ERR versus 0.56). The opposite trend was observed for the other traits. GS did not predict the stability of the quality traits except for flour protein, lactic acid and softness equivalent. Significant GS accuracy for some trait stability indicated that stability was under genetic control for these traits. The magnitude of GS accuracies for all the traits and most of the trait stability index suggests the possibility of rapid selection for these trait and trait stability in wheat breeding.

In the soft red winter wheat (Triticum aestivum L.) regions of the US, Fusarium head blight (FHB, caused by Fusarium spp.) resistance derived from locally adapted germplasm has been used predominantly. Two soft red winter wheat cultivars, Massey and Ernie, have moderate resistance to FHB. Mapping populations derived from Becker/Massey (B/M) and Ernie/MO 94-317 (E/MO) were evaluated for FHB resistance and other traits in multiple environments. Eight QTL in B/M and five QTL in E/MO were associated with FHB variables including incidence, severity (SEV), index (IND), Fusarium damaged kernels (FDK), deoxynivalenol (DON), and morphological traits flowering time and plant height. Four QTL were common to both populations. Three of them were located at or near known genes: Ppd-D1 on chromosome 2DS, Rht-B1 on 4BS, and Rht-D1 on 4DS. Alleles for dwarf plant height (Rht-B1b and Rht-D1b) and photoperiod insensitivity (Ppd-D1a) had pleiotropic effects in reducing height and increasing FHB susceptibility. The other QTL detected for FHB variables were on 3BL in both populations, 1AS, 1DS, 2BL, and 4DL in B/M, and 5AL (B1) and 6AL in E/MO. The additive effects of FHB variables ranged from 0.4 mg kg−1 of DON to 6.2 % for greenhouse (GH) SEV in B/M and ranged from 0.3 mg kg−1 of DON to 8.3 % for GH SEV in E/MO. The 4DS QTL had epistasis with Ppd-D1, Qdon.umc-6AL, and Qht.umc-4BS, and additive × additive × environment interactions with the 4BS QTL for SEV, IND, and FDK in E/MO. Marker-assisted selection might be used to enhance FHB resistance through selection of favorable alleles of significant QTL, taking into account genotypes at Rht-B1b, Rht-D1a and Ppd-D1a.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-013-2149-y) contains supplementary material, which is available to authorized users.

Fusarium head blight (FHB), primarily caused by Fusarium graminearum Schwabe [telemorph: Gibberella zeae Schw. (Petch)], can significantly reduce the grain quality of wheat (Triticum aestivum L.) due to mycotoxin contamination. Two US soft red winter wheat cultivars, Bess and NC‐Neuse, have moderate resistance to FHB. The objective of this study was to validate genomic regions associated with FHB resistance identified in previous studies involving NC‐Neuse and the cultivar Truman, a full‐sib of Bess. A total of 98 doubled haploid lines derived from the cross Bess × NC‐Neuse were evaluated in inoculated, mist‐irrigated field nurseries. The lines were evaluated for FHB incidence, severity, Fusarium‐damaged kernels, and deoxynivalenol content in seven environments between 2011 and 2014. A 3338‐cM linkage map was developed based on 4014 simple sequence repeat and single nucleotide polymorphism markers. Twelve quantitative trait loci (QTL) associated with FHB resistance were identified. NC‐Neuse alleles provided resistance at QTL on five chromosomes and Bess alleles provided resistance at QTL on five other chromosomes. Alignment of linkage maps revealed that five of these QTL were overlapping with previously identified regions. Quantitative trait loci on chromosomes 1A, 4A, and 6A identified in this study overlapped with QTL regions identified in NC‐Neuse, and QTL identified on chromosomes 2B and 3B overlapped with QTL regions identified in Truman. A preliminary test using Kompetitive Allele‐Specific polymerase chain reaction assays on recent Uniform Southern Winter Wheat Scab Nursery entries showed that the assays developed for Qfhb.nc‐2B.1 may be good candidates for use in marker‐assisted selection.

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [telomorph:Gibberella zeae Schw. (Petch)], is an increasingly important disease of wheat (Triticum aestivum L.). Host-plant resistance is considered to be the most economical means of control, but a lack of unique sources of resistance has hindered efforts to breed resistant varieties. The soft red winter wheat, Ernie, has moderately high FHB resistance and is widely used in U.S. breeding programs; however, the genetics of resistance have not been studied. The objectives of this study were to estimate the genetic effects, gene numbers, and heritability for traits related to FHB resistance in Ernie through generation means analyses and variance analyses of 243 F3-derived F8 and F9 recombinant inbred lines (RILs). Replicated experiments were grown in the greenhouse, inoculated with F. graminearum, and evaluated for disease spread and the FHB index (FHBI). The latter was calculated as the percentage of diseased spikelets in inoculated spikes and is often referred to as type-II resistance. Gene action for both disease spread and FHBI was primarily additive with partial dominance for low disease. Broad-sense heritabilities for spread and FHBI were 78.2% and 78.3%, respectively, while the narrow-sense heritabilities were 51.3% and 55.4%, respectively. Line-mean heritabilities from analyses of variance of RILs were 0.70 and 0.87 for spread and FHBI, respectively. A minimum of four genes conditioned both disease spread and FHBI. These results suggest that breeders should be able to enhance FHB resistance by combining the resistance in Ernie with other complementary additive sources of resistance.

A large environmental influence on phenotypic estimates of disease resistance and the complex polygenic nature of Fusarium head blight (FHB) resistance in wheat (Triticum aestivum) are impediments to developing resistant cultivars. The objective of this research was to investigate the utility of a detached leaf assay, inoculated using inoculum from isolates of Microdochium nivale var. majus, to identify components of FHB resistance among 30 entries of U.S. soft red winter wheat in the 2002 Uniform Southern FHB Nursery (USFHBN). Whole plant FHB resistance of the USFHBN entries was evaluated in replicated, mist-irrigated field trials at 10 locations in eight states during the 2001-2002 season. Incubation period (days from inoculation to the first appearance of a dull gray-green water-soaked lesion) was the only detached leaf variable significantly correlated across all FHB resistance parameters accounting for 45% of the variation in FHB incidence, 27% of FHB severity, 30% of Fusarium damaged kernels, and 26% of the variation in grain deoxynivalenol (DON) concentration. The results for incubation period contrasted with previous studies of moderately resistant European cultivars, in that longer incubation period was correlated with greater FHB susceptibility, but agreed with previous findings for the Chinese cultivar Sumai 3 and CIMMYT germ plasm containing diverse sources of FHB resistance. The results support the view that the detached leaf assay method has potential for use to distinguish between specific sources of FHB resistance when combined with data on FHB reaction and pedigree information. For example, entry 28, a di-haploid line from the cross between the moderately resistant U.S. cultivar Roane and the resistant Chinese line W14, exhibited detached leaf parameters that suggested a combination of both sources of FHB resistance. The USFHBN represents the combination of adapted and exotic germ plasm, but four moderately resistant U.S. commercial cultivars (Roane, McCormick, NC-Neuse, and Pat) had long incubation and latent periods and short lesion lengths in the detached leaf assay as observed in moderately FHB resistant European cultivars. The dichotomy in the relationship between incubation period and FHB resistance indicates that this may need to be considered to effectively combine exotic and existing/adapted sources of FHB resistance.