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.

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.

Genome-wide association studies (GWAS) provide an opportunity to examine the genetic architecture of quantitatively inherited traits in breeding populations. The objectives of this study were to use GWAS to identify chromosome regions governing traits of importance in six-rowed winter barley (Hordeum vulgare L.) germplasm and to identify single-nucleotide polymorphisms (SNPs) markers that can be implemented in a marker-assisted breeding program. Advanced hulled and hulless lines (329 total) were screened using 3,072 SNPs as a part of the US. Barley Coordinated Agricultural Project (CAP). Phenotypic data collected over 4 years for agronomic and food quality traits and resistance to leaf rust (caused by Puccinia hordei G. Otth), powdery mildew [caused by Blumeria graminis (DC.) E.O. Speer f. sp. hordei Em. Marchal], net blotch (caused by Pyrenophora teres), and spot blotch [caused by Cochliobolus sativus (Ito and Kuribayashi) Drechsler ex Dastur] were analyzed with SNP genotypic data in a GWAS to determine marker-trait associations. Significant SNPs associated with previously described quantitative trait loci (QTL) or genes were identified for heading date on chromosome 3H, test weight on 2H, yield on 7H, grain protein on 5H, polyphenol oxidase activity on 2H and resistance to leaf rust on 2H and 3H, powdery mildew on 1H, 2H and 4H, net blotch on 5H, and spot blotch on 7H. Novel QTL also were identified for agronomic, quality, and disease resistance traits. These SNP-trait associations provide the opportunity to directly select for QTL contributing to multiple traits in breeding programs.

Many quantitative trait loci (QTL) in wheat {Triticum aestivum L.) conferring resistance to Fusarium head blight (FHB), caused by the Fusarium graminearium, have been mapped in diverse genetic sources. Use of nonadapted FHB resistant sources by breeding programs in the soft red winter (SRW) wheat region of the United States has not been very successful. Therefore, native sources of FHB resistance identified or validated in SRW wheat cultivars predominantly have been used. The breeding line VAOOW-38 has moderate FHB resistance and does not possess any previously identified exotic sources of resistance in its parentage. A set of 182 recombinant inbred lines (RILs) were developed from the cross VAOOW-38 X Pioneer brand '26R46' and tested in field scab nurseries and natural conditions in two environments for each of 2 yr. Eight consistent QTL were identified on chromosomes 1BL, 2A, 2DL, 5B, 6A, and 7A and explained 6.5 to 21.3% of phenotypic variation of traits associated with FHB resistance. Their logarithm of odds (LOD) scores ranged from 2.5 to 6.7. Favorable alíeles to decrease FHB are from VAOOW-38 except one QTL on chromosome 7A. Major QTL on chromosomes 2DL, 6A, and 5B decreased FHB index (IND), Fusarium damaged kernels (FDK), and deoxynivalenol (DQN), respectively. Tightly linked markers identified for these consistent QTL can be used to select for favorable alíeles associated with FHB resistance in breeding populations after validation in diverse genetic backgrounds.

‘Jamestown’ (Reg. No. CV‐1041, PI 653731) soft red winter wheat (Triticum aestivum L.) was developed and released by the Virginia Agricultural Experiment Station in March 2007. Jamestown was derived from the cross ‘Roane’/Pioneer Brand ‘2691’ and was tested under the experimental number VA02W‐370. Jamestown is an early heading, awned, short‐stature, semidwarf (Rht2) cultivar possessing resistance to the predominant insect and disease pests in the eastern soft wheat region. Jamestown most notably has resistance to Hessian fly [Mayetiola destructor (Say)], stripe rust (caused by Puccinia striiformis Westend.), and Fusarium head blight [caused by Fusarium graminearum (Schwabe)]. In USDA–ARS Uniform Southern Soft Red Winter Wheat Nursery Trials conducted at 27 locations in 2005 and at 26 locations in 2006, Jamestown produced average grain yields of 5496 and 5563 kg ha−1, respectively, compared with nursery mean yields of 4959 kg ha−1 in 2005 and 4878 kg ha−1 in 2006. Milling and baking quality of Jamestown exceeds that of ‘USG 3209’. On an Allis Chalmers Mill, Jamestown has higher break flour yield (305 vs. 283 g kg−1), softer flour texture (softness equivalent score 57.4 vs. 54.1 g 100 g−1), lower sucrose solvent retention capacity (93.8 vs. 104 g 100 g−1), and larger cookie diameters (17.0 vs. 16.8 cm).

mayr et al., 1996, Bai et al., 2001, Mesterhazy et al., 1999. Resistance to FHB is considered to be a quantita-Fusarium graminearum Schwabe, the causative agent of Fusarium tive trait and is therefore likely governed by several head blight (FHB), is an economically important pathogen of wheat (Triticum aestivum L.). Breeding FHB resistant wheat requires genes (Buerstmayr et al., 1999). A number of studies knowledge of the underlying genetic control of FHB resistance. While

This chapter focuses on the economic importance, geographical distribution and effects on wheat yield and quality of the wheat powdery mildew pathogen Blumeria graminis f.sp. tritici. The identification of resistance genes and breeding and deployment of wheat powdery mildew resistance are discussed and the morphological and chemical bases of resistance are pointed out. The advantages of the genetic transformation of wheat to improve its resistance to B. graminis f.sp. tritici are also highlighted.

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe can cause extensive losses in wheat (Triticum aestivum L.) seed quality and yield. Greenhouse studies were conducted in 2000 and 2001 to investigate the movement of F. graminearum into floral components of the wheat spike following point inoculation (PI) of a middle floret. The visual greenhouse rating of spikelet infection (severity) following PI for all genotypes in the Uniform Northern and Southern FHB Screening Nurseries with various levels of Type II resistance was also related to seed infection by F. graminearum in the same spikes and to field infection of all genotypes in 2001. Greenhouse ratings of FHB spikelet infection were poorly associated with F. graminearum infection in seeds and other floral components from the same spikelets. Pathogen movement was primarily localized around the PI (resistant cultivars) or moved basally from the PI (susceptible cultivars). Greenhouse FHB spikelet infection ranged from 5 (resistant genotypes) to 100% (susceptible genotypes) with a wide but unrelated range in seed infection in the same spikes. Thus, Type II resistance to FHB (measured by spikelet severity) in the greenhouse was not a good indicator of F. graminearum seed infection. Seed infection with F. graminearum exceeded 70% in all genotypes when grown under near epidemic conditions in the field nursery and was poorly related to visual measurements (spikelet severity and scabby seeds) of Type II resistance. It is proposed that a greenhouse rating of those spikes having <30% spikelet FHB infection can be combined with a laboratory evaluation of the same spikes with <30% F. graminearum seed infection to provide a more definitive method of selecting for Type II resistance.