QTL mapping and marker-assisted selection for Fusarium head blight resistance in wheat: a review

During the past decade, numerous studies have been published on molecular mapping of Fusarium head blight (FHB) resistance in wheat. We summarize the relevant findings from 52 quantitative trait loci (QTL) mapping studies, nine research articles on marker-assisted selection and seven on marker-assisted germplasm evaluation. QTL for FHB resistance were found on all wheat chromosomes except chromosome 7D. Some QTL were found in several independent mapping studies indicating that such QTL are stable and therefore useful in breeding programmes. We summarize and update current knowledge on the genetics of FHB resistance in wheat resulting from QTL mapping investigations and review and suggest FHB breeding strategies based on the available information and DNA markers.     

QTL analysis of resistance to Fusarium head blight in wheat using a 'Wangshuibai'-derived population

Fusarium head blight (FHB) is a devastating disease that reduces the yield, quality and economic value of wheat. For quantitative trait loci (QTL) analysis of resistance to FHB, F₃ plants and F_3:5 lines, derived from a ‘Wangshuibai’ (resistant)/‘Seri82’(susceptible) cross, were spray inoculated during 2001 and 2002, respectively. Artificial inoculation was carried out under field conditions. Of 420 markers, 258 amplified fragment length polymorphism and 39 simple sequence repeat (SSR) markers were mapped and yielded 44 linkage groups covering a total genetic distance of 2554 cM. QTL analysis was based on the constructed linkage map and area under the disease progress curve. The analyses revealed a QTL in the map interval Xgwm533‐Xs18/m12 on chromosome 3BS accounting for up to 17% of the phenotypic variation. In addition, a QTL was detected in the map interval Xgwm539‐Xs15/m24 on chromosome 2DL explaining up to 11% of the phenotypic variation. The QTL alleles originated from ‘Wangshuibai’ and were tagged with SSR markers. Using these SSR markers would facilitate marker‐assisted selection to improve FHB resistance in wheat.     

Comparison of rye,triticale, durum wheat and bread wheat genotypes for Fusarium head blight resistance and deoxynivalenol contamination

Small-grain winter cereal crops can be infected with Fusarium head blight (FHB) leading to mycotoxin contamination and reduction in grain weight and quality. Although a number of studies have investigated the genetic variation of genotypes within each small-grain cereal, a systematic comparison of the winter crops rye, triticale, durum and bread wheat for their FHB resistance, Fusarium-damaged kernels (FDK) and deoxynivalenol (DON) contamination across species is still missing. We have therefore evaluated twelve genotypes each of four crops widely varying in their FHB resistance under artificial infection with one DON-producing F. culmorum isolate at constant spore concentrations and additionally at crop-specific concentrations in two environments. Rye and triticale were the most resistant crops to FHB followed by bread and durum wheat at constant and crop-specific spore concentrations. On average, rye accumulated the lowest amount of DON (10.08 mg/kg) in the grains, followed by triticale (15.18 mg/kg) and bread wheat (16.59 mg/kg), while durum wheat had the highest amount (30.68 mg/kg). Genotypic variances within crops were significant (p ≤ .001) in most instances. These results underline the differing importance of breeding for FHB resistance in the different crops.     

Nature of wheat resistance to Fusarium head blight and the role of deoxynivalenol for breeding

Twenty (1990-93) and 25 (1994-96) wheat genotypes with different degrees of resistance and origins were tested with seven and eight isolates, respectively, of Fusarium graminearum and four Fusarium culmorum isolates of diverse origin in Europe. Infection severity depended largely on the genotypes and the isolates used. Head blight values, yield response and kernel infection values revealed close but varying relationships with deoxynivalenol (DON) content. This variability is explained by the presence of tolerance mechanisms which affect the relationship between Fusarium head blight severity and yield response. Kernel infection resistance accounted for decreasing Fusarium head blight values. Genotypes were found with lower infection severity and higher DON contamination and vice versa. Evidently, the cultivar has a significant influence on DON production in the infected tissue, i.e. highly susceptible genotypes may have moderate or low accumulation of DON. However, in the most resistant genotypes showing no infection to any of the isolates or only sporadic symptom development, no or very low accumulation of DON was detected. Resistant genotypes gave a stable reaction with b-values close to zero for all traits tested. Susceptible genotypes were unstable under different epidemic conditions and their stability was different for the traits investigated. Therefore, the mean of b-values is suggested to better describe the stability of the wheat genotypes. Significant positive relationships were found between aggressiveness of the isolates and their production of DON in the infected grain. The correlation improved significantly for the nivalenol-producing isolate (F89.4 from France) when the sum of DON and nivalenol contents were considered. This indicates that the total trichothecene toxin-producing capacity of the isolates may be a decisive component of pathogenicity. Since the tests included isolates from different European countries the results provide further proof that no host specificity exists within these pathogens in Europe. This was also valid for kernel infection, yield response and DON accumulation. Therefore, the nature of resistance is horizontal. The results also support the view that there is no difference between the resistance of the host plant to F. graminearum and to F. culmorum.     

小麦品种扬麦16赤霉病抗扩展QTL定位及分析

扬麦系列品种赤霉病抗性在世界范围内得到重视,但其抗性遗传机制尚不清楚。扬麦16是近年来大面积推广的抗赤霉病品种,本研究以扬麦16与中麦895杂交构建的174个双单倍体(doublehaploidlines,DH)系为材料,于2017—2019年连续3年对该群体采用单花滴注进行赤霉病抗扩展鉴定。利用660KSNP芯片构建高密度遗传图谱,共检测到6个抗性QTL,分别位于2DL、3BL、4BS、4DS、5BL和6AS染色体上。除4BS位点外,其他5个抗性等位基因均来源于扬麦16。QFhb.yaas-4DS和QFhb.yaas-6AS均在多年被检测到,可解释8.8%～15.0%的表型变异;QFhb.yaas-2DL、QFhb.yaas-3BL仅在1年被检测到,分别解释10.5%和14.7%的表型变异;QFhb.yaas-5BL和来源于中麦895的QFhb.yaas-4BS仅在1年被检测到且效应仅为6.4%和8.3%。QTL效应分析结果表明,相较于单个位点,多个抗性QTL的聚合可显著降低赤霉病严重度。扬麦16抗赤霉病QTL将为揭示扬麦品种抗性遗传机制及开发相应分子标记奠定基础。     

Mapping of QTL for resistance against Fusarium head blight in the winter wheat population Pelikan//Bussard/Ning8026

We report on the identification of FHB ( Fusarium head blight) resistance quantitative trait loci (QTL) of the donor 'G93010' (Bussard/Ning8026) in the background of elite breeding material adapted to the central European climate. With a multiple interval mapping method, two major resistance QTL were identified. Qfhs.lfl-7BS/5BL and Qfhs.lfl-6BS reduced FHB severity individually by 30% and 24%. The combination of both QTL decreased disease severity most effectively by about one half. Qfhs.lfl-6BS is most likely identical to Fhb2 , thus, the effectiveness of Fhb2 in central European breeding material has been validated. Qfhs.lfl-7BS/5BL overlapped with QTL for plant height and heading date. Nevertheless, the selection of lines combining a good FHB resistance level with an acceptable plant height was possible. As the donors of the QTL have probably not yet been utilized in European breeding material, we identified well-adapted lines of the mapping population as valuable donors for marker-assisted breeding programmes.     

Molecular mapping of quantitative trait loci for field resistance to Fusarium head blight in a European winter wheat population

Fusarium head blight (FHB), one of the most destructive diseases of wheat in many parts of the world, can reduce the grain quality due to mycotoxin contamination up to rejection for usage as food or feed. Objective of this study was to map quantitative trait loci (QTL) associated with FHB resistance in the winter wheat population ‘G16‐92’ (resistant)/‘Hussar’. In all, 136 recombinant inbred lines were evaluated in field trials in 2001 and 2002 after spray inoculation with a Fusarium culmorum suspension. The area under disease progress curve was calculated based on the visually scored FHB symptoms. For means across all environments two FHB resistance QTL located on chromosomes 1A, and 2BL were identified. The individual QTL explained 9.7% and 14.1% of the phenotypic variance and together 26.7% of the genetic variance. The resistance QTL on 1A coincided with a QTL for plant height in contrast to the resistance QTL on 2BL that appeared to be independently inherited from morphological characteristics like plant height and ear compactness. Therefore, especially the QTL on 2BL could be of great interest for breeding towards FHB resistance.     

Resistance to Fusarium crown rot in wheat and barley: a review

Fusarium crown rot (FCR) is becoming a major disease in many parts of the cereal‐growing regions worldwide. Significant QTL conferring FCR resistance have been reported on 13 of the 21 possible hexaploid wheat chromosomes in wheat and on three of the seven chromosomes in barley. Available results show that host resistance to FCR is not pathogen species‐specific, that resistance QTL have strong additive effect and that both plant height and growth rate affect FCR severity. Further, different loci seem to be responsible for resistances to FCR and Fusarium head blight although both diseases can be caused by the same Fusarium pathogens. Although marker‐assisted selection for FCR resistance has been initiated, the available markers are all derived from QTL mapping, which provides only limited resolution. Further work has to be conducted in developing diagnostic markers before significant progress can be made in deploying marker‐assisted selection as a routine tool to accelerate and improve FCR in breeding programmes.     

Diallel analysis of resistance to head blight caused by Fusarium culmorum in winter wheat

Summary Ten homozygous winter wheat genotypes representing different levels of resistance to Fusarium head blight were crossed in all possible combinations excluding reciprocals. Parents, F₁ and F₂ were inoculated with one pathogenic strain of Fusarium culmorum. Data for head blight, observed 21 days after first inoculation (OBS-2), and for the area under the disease progress curve, based on observations 14, 21 and 28 days after first inoculation (AUDPC), were analyzed. The contrast between parents and F₁ crosses indicated dommance effects of the resistance genes. Diallel analysis according to Griffing's Method 4, Model 1 showed significant general combining ability (GCA) effects for both F₁ and F₂; specific combining ability effects were not significant. With the exception of one genotype for which general performance for Fusarium resistance was not in agreement with its GCA, the resistance to F. culmorum was uniformly transmitted to all offspring, and the parents can be described in terms of GCA. It is suggested that in the progenies with one of the awned lines as parent, one resistance gene was linked with the gene coding for presence of awns, located on chromosome 4B. A single observation date, taken at the right time, was as effective in assessing resistance as the AUDPC.     

Selection for Fusarium head blight resistance in early generations reduces the deoxynivalenol (DON) content in grain of winter and spring wheat

Fusarium head blight (FHB) results in yield losses and contamination of kernels by mycotoxins, particularly deoxynivalenol (DON). For minimizing DON content in grain, indirect selection methods would increase gains from selection compared to the costly and time‐consuming DON analysis. The aim of this study was to examine whether an early selection for fewer FHB symptoms would lead to a reduced DON content in grain after inoculation with Fusarium culmorum. Starting with a double‐cross derived population of about 1,100 genotypes, 30 F_1:3 genotypes were selected for FHB rating in a two‐step selection in spring wheat with the non‐adapted resistance sources CM82036 and ‘Frontana’. In winter wheat, 30 F_1:2 genotypes were selected out of a double‐cross derived population of about 600 F₁ plants from crosses with German resistance sources (‘Dream’, G16‐92). Selected genotypes were grouped in three categories according to their FHB rating (low, moderate and high) and analysed afterwards for grain DON content. The three groups differed in their DON content illustrating that indirect selection should already be feasible in the earliest generations. Because of the wide genotypic ranges for DON contents within one grouping, a final DON analysis for selected materials is advisable to achieve full selection gain.     

Effect of the Rht-D1 dwarfing locus on Fusarium head blight rating in three segregating populations of winter wheat

Fusarium head blight (FHB) is one of the major fungal diseases in wheat throughout the world. To control FHB severity, breeding genetically resistant varieties is thought to be the most promising strategy. In wheat breeding programmes, short cultivars predominantly carrying the Norin 10 derived semi-dwarfing allele Rht-D1b ( Rht2 ) are preferred worldwide because of higher achievable grain yields and lower risk of lodging. This study was conducted to determine the influence of different alleles at the Rht-D1 locus on FHB reaction. Three winter wheat populations were produced by crossing rather susceptible varieties 'Biscay', 'Pirat' and 'Rubens' carrying mutant-type allele Rht-D1b with the more resistant varieties 'Apache', 'Romanus' and 'History' containing the Rht-D1a wild-type allele ( rht2 ). The 190, 216 and 103 progeny of the F₄-derived populations were assayed for the presence of Rht-D1a or Rht-D1b , plant height, and mean FHB rating after spray inoculation at flowering time with a highly aggressive isolate of Fusarium culmorum . Comparably, high mean FHB severities ranging from 28% to 49% for all population × environment combinations were achieved, with significant genotypic variation for FHB rating and plant height within all populations. Both traits were negatively correlated with r ranging from −0.48 to −0.61 in the complete populations. However, within the subpopulations homozygous for one or other height allele these correlations decreased considerably. The Rht-D1b semi-dwarfing allele resulted in 7–18% shorter plants, depending on the population, but a considerably increased FHB reaction of 22–53%. Nevertheless, significant genotypic variance for FHB resistance remained in all tested Rht-D1b subpopulations indicating that selection for moderately FHB resistant genotypes within agronomically beneficial Rht-D1b genotypes is still feasible.     

Phenotypic selection for high resistance to Fusarium head blight after introgression of quantitative trait loci (QTL) from exotic spring wheat and verification by simple sequence repeat markers a posteriori

Fusarium head blight (FHB) has become an important disease of wheat. We introgressed three resistance quantitative trait loci (QTL) alleles on chromosomes 3B, 5A (from CM82036) and 3A (from ‘Frontana’) into European elite spring wheat and performed phenotypic selection among double‐cross (DC) derived progeny in generations DCF₂ and DCF₃. After recombination and selfing, we analysed 135 phenotypically selected progeny by simple sequence repeat (SSR) markers linked to the QTL. In a second experiment, we forwarded the best 20 progeny for a further two generations by pedigree selection. Progeny were inoculated at two to four locations with Fusarium culmorum and the percentage of infected spikelets per plot was estimated. Both experiments show that phenotypic selection was highly effective. One‐hundred out of 135 phenotypically selected DCF_1:3 progeny had the combination of donor‐QTL alleles (3B + 5A + 3A, 3B + 5A) with the highest effects on FHB resistance. In the subsequent generations, sufficient genotypic variance was detected. The best F_5:7 bulks had similar resistance to the donor CM82036. The FHB rating was reduced in total by 45% points compared to the parental mean. QTL with high effects can be detected solely by phenotypic selection after targeted introgression.     

Genetic variation for resistance to Fusarium head blight in bread wheat

Summary During a four year period, a total of 258 winter and spring wheat genotypes were evaluated for resistance to head blight after inoculation with Fusarium culmorum strain IPO 39-01. It was concluded that genetic variation for resistance is very large. Spring wheat genotypes which had been reported to be resistant to head blight caused by Fusarium graminearum were also resistant to F. culmorum. The resistant germplasm was divided into three gene pools: winter wheats from Eastern Europe, spring wheats from China/Japan and spring wheats from Brazil. In 32 winter wheat genotypes in 1987, and 54 winter wheat genotypes in 1989, the percentage yield reduction depended on the square root of percentage head blight with an average regression coefficient of 6.6. Heritability estimates indicated that for selection for Fusarium head blight resistance, visually assessed head blight was a better selection criterion than yield reduction.     

Chromosomal location of Fusarium head blight resistance genes and analysis of the relationship between resistance to head blight and brown foot rot

In order to identify chromosomes involved in resistance to Fusarium head blight, a set of 21 substitution lines of Triticum macha (resistant) chromosomes into ‘Hobbit’'sib’(susceptible) were evaluated in trials over 2 years. For the first year's trial, all plants were inoculated on the same day with a conidial suspension of F. culmorum. For the second trial, individual plants were inoculated precisely at mid anthesis of each plant over a period of 2 weeks. The disease level was assessed by visual scoring, relative ear weight and F. culmorumn‐specfic quantitative polymerase chain reaction. The results showed that T. macha chromosomes 1B, 4A and 7A conferred good overall resistance, suggesting that they carry important genes for resistance. In two additional trials, T. macha and ‘Hobbit’'sib’ were evaluated for resistance to brown foot rot. The results showed that T. macha was more susceptible than ‘Hobbit’‘sib’, indicating that stem base disease response is not correlated with head blight resistance in these cultivars.     

小偃麦衍生品系的赤霉病抗性评价

由镰孢属(Fusarium)真菌侵染引起的赤霉病是严重威胁小麦生产的重要病害之一,但小麦育种中可直接利用的抗源非常有限。采用单花滴注法接种赤霉菌株F0609,对来源于中间偃麦草或长穗偃麦草的119份小偃麦衍生品系进行3年6个环境的抗病鉴定,发现平均病小穗率<10%的材料有13份,抗性评价为抗病(R);平均病小穗率介于10%~25%之间的材料有61份,抗性评价为中抗(MR);其余45份材料的平均病小穗率介于25%~50%或>50%,抗性评价为中感或高感(MS和S)。在13份高抗赤霉病材料中,CH16387的抗性显著优于苏麦3号和望水白,CH16371和CH16379的抗性显著优于望水白,其余10个品系与抗病对照苏麦3号和望水白的抗性水平相当。这13份材料分别来自小麦-中间偃麦草部分双二倍体TAI8045和小麦-长穗偃麦草部分双二倍体TAP8430与普通小麦的杂交组合,TAI8045抗性显著优于对照品种望水白, TAP8430与苏麦3号和望水白的抗性相当,而杂交组合中的小麦亲本对赤霉病表现感病,推测这些材料的抗性可能来自TAI8045和TAP8430。这些抗病材料为小麦抗赤霉病育种提供了新的种质资源。     

The inheritance of resistance to head blight caused by Fusarium culmorum in winter wheat

Summary Crosses were made among ten winter wheat genotypes representing different levels of resistance to Fusarium head blight to obtain F₁ and F₂ generations. Parents, F₁ and F₂ were inoculated with one strain of Fusarium culmorum. Data on incidence of head blight 21 days after first inoculation were analyzed. Broad-sense heritabilities averaged 0.39 and ranged from 0.05 to 0.89 in the individual F₂ families. The joint-scaling test indicated that the inheritance of Fusarium head blight resistance was adequately described by the additive-dominance model, with additive gene action being the most important factor of resistance. With respect to the non-additive effects, dominance of resistance predominated over recessiveness. The number of segregating genes governing resistance in the studied populations was estimated to vary between one and six. It was demonstrated that resistance genes differed between parents and affected resistance differently.     

Expression of a Triticum turgidum var. dicoccoides source of Fusarium head blight resistance transferred to synthetic hexaploid wheat

Yield and quality reductions caused by Fusarium head blight (FHB) have spurred spring wheat (Triticum aestivum L.) breeders to identify and develop new sources of host plant resistance. Four wheat synthetic hexaploids (×Aegilotriticum sp.) were developed, each having a quantitative trait locus (QTL), Qfhs.ndsu‐3AS, providing FHB resistance from Triticum turgidum L. var. dicoccoides chromosome 3A. Synthetics were produced by hybridizing a ‘Langdon’‐T. dicoccoides‐ recombinant chromosome 3A substitution line (2n = 4x = 28, AABB with two accessions of T. tauschii (2n= 2x = 14, DD). Synthetics were inoculated and evaluated for FHB resistance in two separate greenhouse seasons. One synthetic, 01NDSWG‐5, exhibited FHB severity ratings of 36% and 32% in the separate seasons, compared with ratings of 9% and 30% for ‘Alsen’, a FHB‐resistant spring cultivar, and ratings of 70% and 96% for ‘McNeal’, a susceptible spring cultivar, respectively. Synthetic × Alsen backcross‐derived lines were produced to initiate combining different sources of FHB resistance.     

QTL analysis of resistance to Fusarium head blight in wheat using a 'Frontana'-derived population

Fusarium head blight (FHB or head scab) has become a major limiting factor for sustainable wheat (Triticum aestivum L.) production around the world. For quantitative trait loci (QTL) analysis of resistance to FHB, F₃ plants and F_{3 : 5} lines, derived from a ‘Frontana’ (moderately resistant)/‘Seri82’ (susceptible) cross, were spray‐inoculated in 2001 and 2002, respectively. Artificial inoculations were carried out under field conditions. Of 273 SSR and AFLP markers, 250 could be mapped and they yielded 42 linkage groups, covering a genetic distance of 1931 cM. QTL analysis was based on the constructed linkage map and area under the disease progress curve (AUDPC). The analyses revealed three consistent QTLs associated with FHB resistance on chromosomes 1BL, 3AL and 7AS explaining 7.9%, 7.7% and 7.6% of the phenotypic variation, respectively, above 2 years. The results confirmed the previously described resistance QTL of ‘Frontana’ on chromosome 3AL. A combination of ‘Frontana’ resistance with ‘Sumai‐3’ resistance may lead to lines with augmented resistance expression.     

Fusarium head blight resistance derived from Lophopyrum elongatum chromosome 7E and its augmentation with Fhb1 in wheat

The objective of this study was to assess the effectiveness of Fusarium head blight (FHB) resistance derived from wheatgrass Lophopyrum elongatum chromosome 7E and to determine whether this resistance can augment resistance in combination with other FHB resistance quantitative trait loci (QTL) or genes in wheat. The ‘Chinese Spring’–Lophopyrum elongatum disomic substitution line 7E(7B) was crossed to three wheat lines: ‘Ning 7840’, L3, and L4. F₂ populations were evaluated for type II resistance with the single‐floret inoculation method in the greenhouse. Simple sequence repeat markers associated with Fhb1 in ‘Ning 7840’ and L4 and markers located on chromosome 7E were genotyped in each population. Marker–trait association was analysed with one‐way or two‐way analysis of variance. The research showed that, in the three populations, the average number of diseased spikelets (NDS) in plants with chromosome 7E is 1.2, 3.1 and 3.2, vs. NDS of 3.3, 7.2 and 9.1 in plants without 7E, a reduction in NDS of 2.1, 4.1 and 5.9 in the respective populations. The QTL on 7E and the Fhb1 gene augment disease resistance when combined. The effect of the QTL on 7E was greater than that on 3BS in this experiment. Data also suggest that the FHB resistance gene derived from L. elongatum is located on the long arm of 7E.