Fusarium head blight is among the most extensively studied fungal diseases of wheat and other small grain cereals due to its impact on yield and quality, but particularly due to its potential to produce mycotoxins, which are harmful to humans and animals. Since our last comprehensive review on QTL mapping and marker‐assisted selection for FHB resistance in wheat in 2009, numerous studies have been conducted to identify, validate or fine‐map resistance QTL. The main aim of this review is to update and summarize findings on FHB resistance breeding of wheat published during the last decade. Furthermore, we compiled a user‐friendly table listing FHB resistance QTL data providing a valuable resource for further FHB resistance research. The role of morphological and phenological traits on FHB resistance and possible consequences for resistance breeding are discussed. This review concentrates current knowledge on breeding for FHB resistance and suggests strategies to enhance resistance by deploying molecular breeding methods, including marker‐assisted and genomic selection.

Fusarium head blight (FHB) is a fungal disease of worldwide importance to small grain cereals that may lead to severe losses in both yield and quality. The development of resistant varieties is the most effective approach for managing the disease. Genetic variation for FHB resistance is large, including 'exotic' and 'native' wheat germplasm. Methods for selecting improved lines include: 1) phenotypic selection with direct symptom evaluation; 2) marker-assisted selection for well-characterized QTL and 3) genomic selection employing genome-wide prediction models. Breeding programs need to find the optimal deployment of the complementary approaches according to their available facilities, resources and requirements. This review aims to summarize recent advances in FHB resistance breeding, thereby discussing the importance of morphological traits like the extent of retained anthers after flowering, its suitability for indirect selection and the pronounced association of the semi-dwarfing allele Rht-D1b with increased anther retention and FHB severity. Markerassisted selection is successfully applied to select for largeeffect QTL, especially for the most prominent resistance QTL Fhb1 in bread wheat, as well as in durum wheat as recently demonstrated. The resistance locus Fhb1 has been partly elucidated, a pore-forming toxin-like gene confers resistance against fungal spread. Genomic selection for FHB resistance appears promising especially for breeding programs deploying 'native' resistance sources with many small-effect QTL.

Breeding for resistance to Fusarium head blight (FHB) in durum wheat continues to be hindered by the lack of effective resistance sources. Only limited information is available on resistance QTL for FHB in tetraploid wheat. In this study, resistance to FHB of a Triticum dicoccum line in the background of three Austrian T. durum cultivars was genetically characterized. Three populations of BC1F4-derived RILs were developed from crosses between the resistant donor line T. dicoccum-161 and the Austrian T. durum recipient varieties DS-131621, Floradur and Helidur. About 130 BC1F4-derived lines per population were evaluated for FHB response using artificial spray inoculation in four field experiments during two seasons. Lines were genetically fingerprinted using SSR and AFLP markers. Genomic regions on chromosomes 3B, 4B, 6A, 6B and 7B were significantly associated with FHB severity. FHB resistance QTL on 6B and 7B were identified in two populations and a resistance QTL on 4B appeared in three populations. The alleles that enhanced FHB resistance were derived from the T. dicoccum parent, except for the QTL on chromosome 3B. All QTL except the QTL on 6A mapped to genomic regions where QTL for FHB have previously been reported in hexaploid wheat. QTL on 3B and 6B coincided with Fhb1 and Fhb2, respectively. This implies that tetraploid and hexaploid wheat share common genomic regions associated with FHB resistance. QTL for FHB resistance on 4B co-located with a major QTL for plant height and mapped at the position of the Rht-B1 gene, while QTL on 7B overlapped with QTL for flowering time.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-1951-2) contains supplementary material, which is available to authorized users.

Key messageFusarium resistance in Arina is highly quantitative and governed by multiple small effect QTL. Anther retention has a high correlation with FHB susceptibility and appears a practicable indirect selection target for enhancing FHB resistance.AbstractThe Swiss winter wheat cultivar Arina possesses a high resistance level constituted by a number of small to medium effect QTL reported from three independent mapping populations. Yet these overlap only for one resistance QTL on the long arm of chromosome 1B. The present study characterized Fusarium head blight (FHB) resistance in a population of 171 recombinant inbred lines from a cross between Arina (resistant) and Capo (moderately resistant). The population was evaluated for FHB resistance under field conditions for 3 years. Additionally, we phenotyped anther retention, plant height and flowering date to analyze their association with resistance. Lines with a low proportion of retained anthers after flowering and tall plants were significantly less diseased, while flowering date had no association with FHB severity. QTL analysis identified eight small to medium effect QTL for FHB severity, of which QTL on 1BS, 3B, 4AL and 6BL likely correspond to resistance alleles already detected in previously studied Arina populations. QTL for anther retention mapped to 4AL, 6BL and 5AS. Notably, QTL on 4AL and 6BL overlapped with QTL for FHB severity. A single small effect QTL for plant height was detected on 5AS and no QTL was identified for flowering date. Genotypes having three or four resistance alleles in combination showed a good resistance level, indicating pyramiding resistance QTL as a powerful approach for breeding resistant cultivars. Selection for rapid and complete anther extrusion appears promising as an indirect selection criterion for enhancing FHB resistance.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2527-8) contains supplementary material, which is available to authorized users.

Key message Fine-mapping separated Qfhs.ifa-5A into a major QTL mapping across the centromere and a minor effect QTL positioned at the distal half of 5AS. Both increase Fusarium resistance and anther extrusion. Abstract The Fusarium head blight (FHB) resistance QTL Qfhs.ifa - 5A resides in the low-recombinogenic pericentromeric region of chromosome 5A making fine-mapping particularly arduous. Qfhs.ifa - 5A primarily contributes resistance to fungal entry with the favorable allele descending from the highly Fusarium resistant cultivar Sumai-3. Fine-mapping a near-isogenic recombinant inbred line population partitioned the Qfhs.ifa - 5A interval into 12 bins. Near-isogenic lines recombining at the interval were phenotyped for FHB severity, anther retention and plant height. Composite interval mapping separated the initially single QTL into two QTL. The major effect QTL Qfhs.ifa - 5Ac mapped across the centromere and the smaller effect QTL Qfhs.ifa - 5AS mapped to the distal half of 5AS. Although Qfhs.ifa - 5Ac and Qfhs.ifa - 5AS intervals were as small as 0.1 and 0.2 cM, their corresponding physical distances were large, comprising 44.1 Mbp and 49.2 Mbp, respectively. Sumai-3 alleles at either QTL improved FHB resistance and increased anther extrusion suggesting a pleiotropic effect of anthers on resistance. This hypothesis was supported by greenhouse experiments using the susceptible cultivar Remus and its resistant near-isogenic line NIL3 carrying the entire Qfhs.ifa - 5A segment. By manually removing anthers prior to spray inoculation both, Remus and NIL3 became almost equally resistant in the early phase of the disease development and were significantly less diseased than variants without anther manipulation. At late time points the positive effect of the anther removal became smaller for Remus and disappeared completely for NIL3. Results affirm that absence of anthers enhanced resistance to initial infection but did not protect plants from fungal spreading within spikes. Electronic supplementary material The online version of this article (10.1007/s00122-019-03336-x) contains supplementary material, which is available to authorized users.

While many reports on genetic analysis of Fusarium head blight (FHB) resistance in bread wheat have been published during the past decade, only limited information is available on FHB resistance derived from wheat relatives. In this contribution, we report on the genetic analysis of FHB resistance derived from Triticum macha (Georgian spelt wheat). As the origin of T. macha is in the Caucasian region, it is supposed that its FHB resistance differs from other well-investigated resistance sources. To introduce valuable alleles from the landrace T. macha into a modern genetic background, we adopted an advanced backcross QTL mapping scheme. A backcross-derived recombinant-inbred line population of 321 BC2F3 lines was developed from a cross of T. macha with the Austrian winter wheat cultivar Furore. The population was evaluated for Fusarium resistance in seven field experiments during four seasons using artificial inoculations. A total of 300 lines of the population were genetically fingerprinted using SSR and AFLP markers. The resulting linkage map covered 33 linkage groups with 560 markers. Five novel FHB-resistance QTL, all descending from T. macha, were found on four chromosomes (2A, 2B, 5A, 5B). Several QTL for morphological and developmental traits were mapped in the same population, which partly overlapped with FHB-resistance QTL. Only the 2BL FHB-resistance QTL co-located with a plant height QTL. The largest-effect FHB-resistance QTL in this population mapped at the spelt-type locus on chromosome 5A and was associated with the wild-type allele q, but it is unclear whether q has a pleiotropic effect on FHB resistance or is closely linked to a nearby resistance QTL.

The semidwarfing alleles reduced height (Rht)-D1b and Rht-B1b are widely deployed in wheat breeding. Both alleles have similar effects on plant height but differ in their effect on Fusarium head blight (FHB) severity. A double-haploid population and a backcross population, segregating for Rht-B1a/Rht-B1b and Rht-D1a/Rht-D1b, were evaluated for FHB severity, plant height, and anther retention in field trials in three consecutive years. The semidwarfing alleles reduced plant height and increased the proportion of retained anthers. Reduced plant height and a high proportion of retained anthers were associated with increased FHB severity. The Rht-D1b allele had a significantly greater impact on anther retention and FHB severity than the Rht-B1b allele. Fusarium graminearum establishes infection sites predominantly inside the floral cavity and retained anthers potentially support colonization and initial hyphal growth, leading to a higher disease level in genotypes with a higher proportion of retained anthers. This is the first report demonstrating that differences in disease severity associated with Rht-D1b and Rht-B1b can be partly explained by their different effect on the extent of anther retention.

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