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.     

Types and components of resistance to Fusarium head blight of wheat

Resistance of wheat to Fusarium head blight caused by Fusarium graminearum and F. culmorum was identified in natural epidemics in 1985 and 1987 as well after artificial inoculations (1983–1988 and 1984–1987). Out of 25 genotypes tested, five were identified with no significant difference in head blight scores, but differing significantly in yield after artificial inoculation, i.e. tolerance differences were detected at different resistance levels. Some genotypes that were similar in yield or head blight scores differed in seed infection severity. Genotypes with awns were more susceptible to head blight when tested under natural epidemic condition in the field; but this trait did not influence head blight severity in artificial inoculations. Dwarf genotypes were more severely infected by head blight than tall genotypes under natural conditions, but genotypes of different plant height classes were similarly susceptible after artificial inoculations. In the early generations of a breeding programme resistance measured by visual evaluation of artificial inoculation is the most important way to screen. If selection of dwarf and awned genotypes cannot be avoided, the higher susceptibility caused by awns and dwarfness under natural epidemic conditions can be decreased by a higher level of physiological resistance, as variability in physiological resistance is available. In later generations, traits like percentage of seed infection or tolerance can be identified by additionally measuring yield reduction. Stability of disease reaction appears to be connected with resistance level, the most resistant genotypes are the most stable, and the most susceptible ones tend to have more unstable reactions in different epidemic conditions.     

Resistance to Fusarium head blight and deoxynivalenol accumulation in wheat

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (telomorph =Gibberella zeae (Schw.)), is an important wheat disease world‐wide. Production of deoxynivalenol (DON) by F. graminearum in infected wheat grain is detrimental to livestock and is also a safety concern in human foods. An international collection of 116 wheat lines was evaluated for FHB resistance and concentration of DON in grain. Plants were inoculated with mixed isolates of F. graminearum in the greenhouse by injecting conidia into a single spikelet of each spike and in the field by scattering F. graminearum‐infected wheat kernels on the soil surface. FHB symptoms were evaluated by visual inspection in both the greenhouse and field, and DON was analysed by HPLC. Significant differences in FHB ratings and DON levels were observed among cultivars. In the greenhouse test, visual symptoms varied from no spread of FHB from the inoculated spikelet to spread throughout the spike, and DON levels ranged from trace levels to 283 mg/kg. In the field test, DON ranged from 2.8 to 52 mg/kg. The greenhouse test identified 16 wheat lines from various origins that accumulated less than 2 mg/kg DON. These lines may be useful as sources for breeding wheat cultivars with lower DON levels. Correlation coefficients were significant between FHB symptom ratings, seed quality traits, and DON levels. Thus, the percentage of scabbed spikelets and kernels can be generally used to predict DON levels in harvested wheat grain. In breeding programmes, selection for plants having few scabbed spikelets and scabbed kernels is most likely to result in low DON levels.     

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.     

A QTL for early heading in wheat cultivar Suwon 92

Heading date is an important trait that determines wheat adaptation to environments. A recombinant inbred line (RIL) population derived from CI 13227 × Suwon 92 was employed to tag the quantitative trait locus (QTL) for early heading in Suwon 92. This population was phenotyped for heading date in 1994, 1995, and 1997, and analyzed with AFLP and SSR markers. Two AFLP markers (XGCTG.CGCT118 and XGCTG.CGCT60) closely associated with heading date were identified. Across years, XGCTG.CGCT118 and XGCTG.CGCT60 explained 40.4% and 32.2% of the total phenotypic variances, respectively. Interval analysis revealed a major QTL for heading date, designated QHd.pser-2DS, between AFLP marker XGCTG.CGCT118 and SSR marker Xgwm261. Based on the linkage map, QHd.pser-2DS was about 41.2 cM proximal to the distal end of chromosome 2DS, and explained 40.5% of the phenotypic variance across three years. The identified markers associated with the early heading QTL have the potential to be used in wheat breeding programs.     

Validation of two major quantitative trait loci for fusarium head blight resistance in Chinese wheat line W14

Identity of quantitative trait loci (QTL) governing resistance to fusarium head blight (FHB) initial infection (type I), spread (type II), kernel infection, and deoxynivalenol (DON) accumulation was characterized in Chinese wheat line W14. Ninety‐six double‐haploid lines derived from a cross of W14 × ’Pion2684’ were evaluated for FHB resistance in two greenhouse and one field experiment. Two known major QTL were validated on chromosomes 3BS and 5AS in W14 using the composite interval mapping method. The 3BS QTL had a larger effect on resistance than the 5AS QTL in the greenhouse experiments, whereas, the 5AS QTL had a larger effect in the field experiment. These two QTL together explained 33%, 35%, and 31% of the total phenotypic variation for disease spread, kernel infection, and DON concentration in the greenhouse experiments, respectively. In the field experiment, the two QTL explained 34% and 26% of the total phenotypic variation for FHB incidence and severity, respectively. W14 has both QTL, which confer reduced initial infection, disease spread, kernel infection, and DON accumulation. Therefore, marker‐assisted selection (MAS) for both QTL should be implemented in incorporating W14 resistance into adapted backgrounds. Flanking markers Xbarc133 and Xgwm493 on 3BS and Xbarc117 and Xbarc56 on 5AS are suggested for MAS.     

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。     

Inheritance of resistance to Fusarium head blight in the wheat lines 'CJ 9306' and 'CJ 9403'

Fusarium head blight (FHB or scab) caused by Fusarium graminearum is a worldwide serious disease in wheat. Exploitation and genetic studies of elite resistance sources can speed up the development of resistant cultivars. To characterize the inheritance of host plant resistance in two new lines, ‘CJ 9306’ and ‘CJ 9403’, developed from a recurrent selection programme in China, six generations P₁, P₂, F₁, F₂, B₁ and B₂ of four crosses and 137 F_{6 : 7} recombinant inbred lines (RILs) from one cross were evaluated in the greenhouse for scab resistance using single‐floret inoculation. The data of area under disease progress curve (AUDPC) in F₂, backcross (BC) and RIL populations exhibited mono‐modal distributions without clear‐cut demarcations and skewing towards resistance. An additive–dominance model was well‐fitted, additive effects played a predominating role, and dominance effects were also significant. Continuous distributions with two major peaks and one minor peak for the number or percentage of scabby spikelets (NSS or PSS) in segregating populations implied the existence of major genes or quantitative trait loci (QTL) for resistance. The estimates of broad‐sense and narrow‐sense heritabilities based on the six‐generation experiment were 56–76% and 26–67% respectively. The estimates of broad‐sense heritabilities based on anova with RILs were 89–90%. These two improved lines with excellent scab resistance and good agronomic traits are of interest for wheat breeding and production.     

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.     

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.     

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.     

Identification of novel QTL for resistance to crown rot in the doubled haploid wheat population 'W21MMT70' × 'Mendos'

Crown rot (causal agent Fusarium pseudograminearum) is a fungal disease of major significance to wheat cultivation in Australia. A doubled haploid wheat population was produced from a cross between line ‘W21MMT70’, which displays partial seedling and adult plant (field) resistance to crown rot, and ‘Mendos’, which is moderately susceptible in seedling tests but partially resistant in field trials. Bulked segregant analysis (BSA) based on seedling trial data did not reveal markers for crown rot resistance. A framework map was produced consisting of 128 microsatellite markers, four phenotypic markers, and one sequence tagged site marker. To this map 331 previously screened AFLP markers were then added. Three quantitative trait loci (QTL) were identified with composite interval mapping across all of the three seedling trials conducted. These QTL are located on chromosomes 2B, 2D and 5D. The 2D and 5D QTL are inherited from the line ‘W21MMT70’, whereas the 2B QTL is inherited from ‘Mendos’. These loci are different from those associated with crown rot resistance in other wheat populations that have been examined, and may represent an opportunity for pyramiding QTL to provide more durable resistance to crown rot.     

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.     

Comparison of evaluation methods for selection of resistance to Fusarium head blight in a recurrent selection programme in wheat (Triticum aestivum L.)

The objectives of this study were to compare efficiency of evaluation for resistance to Fusarium head blight (FHB) under two inoculation methods in a recurrent selection programme. Fifty selected homozygous F₅ fertile lines, from each of five cycles (C0, C1, C2, C3 and C4) of recurrent selection, and two control cultivars were evaluated in a split-plot design in 1995 and 1996 under the soil-surface inoculation with Fusarium graminearum-colonized kernels and the single-floret inoculation with ascospore suspension. Comparison of the two inoculation methods using means, ranges, coefficients of variation, heritabilities and correlations among infected spikelet rate (ISR), reaction index (RI) and disease index (DI) indicated that FHB resistance could be evaluated with similar accuracy and precision using either of the two inoculation methods. Regressions of disease scores in the soil-surface inoculation on disease scores in the single-surface inoculation were positive and highly significant, showing a strong relationship between both inoculation methods for FHB resistance. The percentage of lines with similar performance for FHB disease scores in both inoculation methods was high. The soil-surface inoculation and single-floret inoculation appear to be useful techniques for evaluating numerous individuals of segregating population and screening advanced homozygous lines for FHB resistance in a recurrent selection programme in wheat, respectively.     

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.     

Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhouse

Fusarium head blight (FHB, scab), caused by Fusarium graminearum Schwabe, is a serious and damaging disease of wheat. Although some hexaploid wheat lines express a good level of resistance to FHB, the resistance available in hexaploid wheat has not yet been transferred to durum wheat. A germplasm collection of Triticum durum× alien hybrid lines was tested as a potential source of resistance to FHB under controlled conditions. Their FHB reaction was evaluated in three tests against conidial suspensions of three strains of F. graminearum at the flowering stage. Two T. durum×Thinopyrum distichum hybrid lines, ‘AFR4’ and ‘AFR5′, expressed a significantly higher level of resistance to the spread of FHB than other durum‐alien hybrid lines and a resistant common wheat line ‘Nyu‐Bay’. Genomic in situ hybridization using total genomic DNA from alien grass species demonstrated that ‘AFR5’ had 13 or 14 alien genome chromosomes plus 27 or 28 wheat chromosomes, while ‘AFR4’ had 22 alien genome and 28 wheat chromosomes. All of the alien chromosomes present in these two lines belonged to the J genome. ‘AFR5’ is likely to be more useful as a source of FHB resistance than ‘AFR4’ because of its relatively normal meiotic behaviour, high fertility and fewer number of alien chromosomes. ‘AFR5’ shows good potential as a source for transferring FHB resistance gene into wheat. The development of T. durum addition lines carrying resistance genes from ‘AFR5’ is underway.     

Validation of a major QTL for scab resistance with SSR markers and use of marker-assisted selection in wheat

The objectives of this study were to validate the major quantitative trait locus (QTL) for scab resistance on the short arm of chromosome 3B in bread wheat and to isolate near‐isogenic lines for this QTL using marker‐assisted selection (MAS). Two resistant by susceptible populations, both using ‘Ning7840’ as the source of resistance, were developed to examine the effect of the 3BS QTL in different genetic backgrounds. Data for scab resistance and simple sequence repeat (SSR) markers linked to the resistance QTL were analyzed in the F_2:3 lines of one population and in the F_3:4 lines of the other. Markers linked to the major QTL on chromosome 3BS in the original mapping population (‘Ning7840’/‘Clark’) were closely associated with scab resistance in both validation populations. Marker‐assisted selection for the QTL with the SSR markers combined with phenotypic selection was more effective than selection based solely on phenotypic evaluation in early generations. Marker‐assisted selection of the major QTL during the seedling stage plus phenotypic selection after flowering effectively identified scab resistant lines in this experiment. Near‐isogenic lines for this 3BS QTL were isolated from the F₆ generation of the cross ‘Ning7840’/‘IL89‐7978’ based on two flanking SSR markers, Xgwm389 and Xbarc147. Based on these results, MAS for the major scab resistance QTL can improve selection efficiency and may facilitate stacking of scab resistance genes from different sources.     

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.     

A major QTL effect controlling resistance to powdery mildew in winter wheat at the adult plant stage

Powdery mildew is one of the major diseases of wheat in regions with a maritime or semi‐continental climate which can strongly affect grain yield. The objective of the study was to identify and compare quantitative resistance to powdery mildew of line RE9001 at the adult plant and vernalized seedling stages. RE9001 has no known Pm gene and shows a high level of adult plant resistance in the field. Using 104 recombinant inbred lines (RILs) of an RE9001 × ‘Courtot’ F8 population, a genetic map was developed with 363 markers distributed over 26 linkage groups and covering 3825 cM. The global map density was 1 locus/10.3 cM. RILs were assessed under field and tunnel greenhouse conditions for 2 years in two locations. Eleven quantitative trait loci (QTL) were detected at the adult stage and they explained 63% of the variation, depending on the environment. Three QTLs were found, at least, in the two environments. One QTL from RE9001, mapped on chromosome 2B, was stable in each environment. This QTL, QPm.inra.2B, explained 10.3–36.6% of the variation and could be mapped in the vicinity of the Pm6 gene. At the vernalized seedling stage, one QTL detected by the isolate 93‐27 could be an allele of the Pm3g gene present in ‘Courtot’. No residual effect of the Pm3g gene was detected at either stage. Markers flanking the QTL 2B could be useful tools to combine resistance to powdery mildew in wheat cultivars.     

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.