Genetic characterization of QTL associated with resistance to Fusarium head blight in a doubled-haploid spring wheat population.

Fusarium head blight (FHB) is one of the most important fungal wheat diseases worldwide. Understanding the genetics of FHB resistance is the key to facilitating the introgression of different FHB resistance genes into adapted wheat. The objectives of the present study were to detect and map quantitative trait loci (QTL) associated with FHB resistance genes and characterize the genetic components of the QTL in a doubled-haploid (DH) spring wheat population using both single-locus and two-locus analysis. A mapping population, consisting of 174 DH lines from the cross between DH181 (resistant) and AC Foremost (susceptible), was evaluated for type I resistance to initial infection during a 2-year period in spray-inoculated field trials, for Type II resistance to fungal spread within the spike in 3 greenhouse experiments using single-floret inoculation, and for resistance to kernel infection in a 2001 field trial. One-locus QTL analysis revealed 7 QTL for type I resistance on chromosome arms 2DS, 3AS, 3BS, 3BC (centromeric), 4DL, 5AS, and 6BS, 4 QTL for type II resistance on chromosomes 2DS, 3BS, 6BS, and 7BL, and 6 QTL for resistance to kernel infection on chromosomes 1DL, 2DS, 3BS, 3BC, 4DL, and 6BS. Two-locus QTL analysis detected 8 QTL with main effects and 4 additive by additive epistatic interactions for FHB resistance and identified novel FHB resistance genes for the first time on chromosomes 1DL, 4AL, and 4DL. Neither significant QTL by environment interactions nor epistatic QTL by environment interactions were found for either type I or type II resistance. The additive effects of QTL explained most of the phenotypic variance for FHB resistance. Marker-assisted selection for the favored alleles at multiple genomic regions appears to be a promising tool to accelerate the introgression and pyramiding of different FHB resistance genes into adapted wheat genetic backgrounds.     

Quantitative trait loci responsible for Fusarium head blight resistance in Chinese landrace Baishanyuehuang

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is a destructive disease that can significantly reduce grain yield and quality. Deployment of quantitative trait loci (QTLs) for FHB resistance in commercial cultivars has been the most effective approach for minimizing the disease losses. 'Baishanyuehuang' is a highly FHB-resistant landrace from China. Recombinant inbred lines (RILs) developed from a cross of 'Baishanyuehuang' and 'Jagger' were evaluated for FHB resistance in three greenhouse experiments in 2010 and 2011 by single-floret inoculation. Percentage of symptomatic spikelets in an inoculated spike was recorded 18 days post-inoculation. The RIL population was screened with 251 polymorphic simple sequence repeats. Four QTLs were associated with FHB resistance and mapped on three chromosomes. Two QTLs were located on the short arm of chromosome 3B (3BS) with one in distal of 3BS and another near centromere (3BSc), designated as Qfhb.hwwg-3BSc. The QTL in the distal of 3BS is flanked by Xgwm533 and Xgwm493, thus corresponds to Fhb1. This QTL explained up to 15.7 % of phenotypic variation. Qfhb.hwwg-3BSc flanked by Xwmc307 and Xgwwm566 showed a smaller effect than Fhb1 and explained up to 8.5 % of phenotypic variation. The other two QTLs were located on 3A, designated as Qfhb.hwwg-3A, and 5A, designated as Qfhb.hwwg-5A. Qfhb.hwwg-3A was flanked by Xwmc651 and Xbarc356 and explained 4.8-7.5 % phenotypic variation, and Qfhb.hwwg-5A was flanked by markers Xgwm186 and Xbarc141, detected in only one experiment, and explained 4.5 % phenotypic variation for FHB resistance. 'Baishanyuehuang' carried all resistance alleles of the four QTL. Qfhb.hwwg-3BSc and Qfhb.hwwg-3A were new QTLs in 'Baishanyuehuang'. 'Baishanyuehuang' carries a combination of QTLs from different sources and can be a new source of parent to pyramid FHB-resistant QTLs for improving FHB resistance in wheat.     

DNA markers for Fusarium head blight resistance QTLs in two wheat populations

Genetic resistance to Fusarium head blight (FHB), caused by Fusarium graminearum, is necessary to reduce the wheat grain yield and quality losses caused by this disease. Development of resistant cultivars has been slowed by poorly adapted and incomplete resistance sources and confounding environmental effects that make screening of germplasm difficult. DNA markers for FHB resistance QTLs have been identified and may be used to speed the introgression of resistance genes into adapted germplasm. This study was conducted to identify and map additional DNA markers linked to genes controlling FHB resistance in two spring wheat recombinant inbred populations, both segregating for genes from the widely used resistance source ’Sumai 3’. The first population was from the cross of Sumai 3/Stoa in which we previously identified five resistance QTLs. The second population was from the cross of ND2603 (Sumai 3/Wheaton) (resistant)/ Butte 86 (moderately susceptible). Both populations were evaluated for reaction to inoculation with F. graminearum in two greenhouse experiments. A combination of 521 RFLP, AFLP, and SSR markers were mapped in the Sumai 3/Stoa population and all DNA markers associated with resistance were screened on the ND2603/Butte 86 population. Two new QTL on chromosomes 3AL and 6AS wer found in the ND2603/Butte 86 population, and AFLP and SSR markers were identified that explained a greater portion of the phenotypic variation compared to the previous RFLP markers. Both of the Sumai 3-derived QTL regions (on chromosomes 3BS, and 6BS) from the Sumai 3/Stoa population were associated with FHB resistance in the ND2603/Butte 86 population. Markers in the 3BS QTL region (Qfhs.ndsu-3BS) alone explain 41.6 and 24.8% of the resistance to FHB in the Sumai 3/Stoa and ND2603/Butte 86 populations, respectively. This region contains a major QTL for resistance to FHB and should be useful in marker-assisted selection. Received: 17 August 2000 / Accepted: 16 October 2000     

Novel quantitative trait loci (QTL) for Fusarium head blight resistance in wheat cultivar Chokwang

Fusarium head blight (FHB) is one of the most destructive diseases in wheat. This study was to identify new quantitative trait loci (QTL) for FHB resistance and the molecular markers closely linked to the QTL in wheat cultivar Chokwang. The primers of 612 simple sequence repeats (SSRs) and 12 target-region-amplified polymorphism (TRAP) marker were analyzed between resistant (Chokwang) and susceptible (Clark) parents. One hundred and seventy-two polymorphic markers were used to screen a population of 79 recombinant inbred lines (RILs) derived from the cross of Chokwang and Clark. One major QTL, Qfhb.ksu-5DL1, was identified on chromosome 5DL. The SSR marker Xbarc 239 was mapped in the QTL region, and also physically located to the bin of 5DL1-0.60-0.74 by using Chinese Spring deletion lines. Another QTL Qfhb.ksu-4BL1was linked to SSR Xbarc 1096 and tentatively mapped on 4BL. A QTL on 3BS, Qfhb.ksu-3BS1, was also detected with marginal significance in this population. Different marker alleles for these QTL were detected between Chokwang and Sumai 3 and its derivatives. These results suggested that Chokwang contains new QTL for FHB resistance that are different from those in Sumai 3. Pyramiding resistance QTL from various sources may enhance FHB resistance in wheat cultivars.     

Haplotype diversity at fusarium head blight resistance QTLs in wheat

Fusarium head blight (FHB) reduces grain yield and quality in common and durum wheat. Host FHB resistance is an effective control measure that is achieved by stacking multiple resistance genes into a wheat line. Therefore, breeders would benefit from knowing which resistance sources carry different resistance genes. A diverse collection of FHB-resistant and -susceptible wheat lines was characterized with microsatellite markers linked to FHB resistance quantitative trait loci (QTLs) on chromosomes 2DL, 3BS (distal to the centromere), 3BSc (proximal to the centromere), 4B, 5AS and 6BS identified in wheat lines Maringa, Sumai 3 and Wuhan 1. Putative Sumai 3 QTLs were commonly observed in advanced breeding lines, whereas putative Maringa and Wuhan 1 QTLs were relatively rare. Marker data suggested the 3BS, 3BSc and 5AS QTLs in the Brazilian cv. Maringa were derived from Asian germplasm and not from Frontana or other Brazilian lines. Haplotype diversity was reduced near the 5AS QTL, which might impact the deployment of this QTL. Finally, Brazilian germplasm was not closely related to other resistance sources and might be useful for pyramiding with Asian wheat-derived FHB resistance.Communicated by J. W. Snape     

Molecular mapping of novel genes controlling Fusarium head blight resistance and deoxynivalenol accumulation in spring wheat.

Fusarium head blight of wheat is an extremely damaging disease, causing severe losses in seed yield and quality. The objective of the current study was to examine and characterize alternate sources of resistance to Fusarium head blight (FHB). Ninety-one F1-derived doubled haploid lines from the cross Triticum aestivum 'Wuhan-1' x Triticum aestivum 'Maringa' were examined for disease reaction to Fusarium graminearum by single-floret injection in replicated greenhouse trials and by spray inoculation in replicated field trials. Field and greenhouse experiments were also used to collect agronomic and spike morphology characteristics. Seed samples from field plots were used for deoxynivalenol (DON) determination. A total of 328 polymorphic microsatellite loci were used to construct a genetic linkage map in this population and together these data were used to identify QTL controlling FHB resistance, accumulation of DON, and agronomic and spike morphology traits. The analysis identified QTL for different types of FHB resistance in four intervals on chromosomes 2DL, 3BS, and 4B. The QTLs on 4B and 3BS proximal to the centromere are novel and not reported elsewhere. QTL controlling accumulation of DON independent of FHB resistance were located on chromosomes 2DS and 5AS. Lines carrying FHB resistance alleles on 2DL and 3BS showed a 32% decrease in disease spread after single-floret injection. Lines carrying FHB resistance alleles on 3BS and 4B showed a 27% decrease from the mean in field infection. Finally, lines carrying favourable alleles on 3BS and 5AS, showed a 17% reduction in DON accumulation. The results support a polygenic and quantitative mode of inheritance and report novel FHB resistance loci. The data also suggest that resistance to FHB infection and DON accumulation may be controlled, in part, by independent loci and (or) genes.     

Molecular mapping of QTL for Fusarium head blight resistance introgressed into durum wheat

Key message

The major QTL for FHB resistance from hexaploid wheat line PI 277012 was successfully introgressed into durum wheat and minor FHB resistance QTL were detected in local durum wheat cultivars. A combination of these QTL will enhance FHB resistance of durum wheat.

Abstract

Fusarium head blight (FHB), caused by Fusarium graminearum, is a devastating disease of durum wheat. To combat the disease, great efforts have been devoted to introgress FHB resistance from its related tetraploid and hexaploid wheat species into adapted durum cultivars. However, most of the quantitative trait loci (QTL) for FHB resistance existing in the introgression lines are not well characterized or validated. In this study, we aimed to identify and map FHB resistance QTL in a population consisting of 205 recombinant inbred lines from the cross between Joppa (a durum wheat cultivar) and 10Ae564 (a durum wheat introgression line with FHB resistance derived from the hexaploid wheat line PI 277012). One QTL (Qfhb.ndwp-2A) from Joppa and two QTL (Qfhb.ndwp-5A and Qfhb.ndwp-7A) from 10Ae564 were identified through phenotyping of the mapping population for FHB severity and DON content in greenhouse and field and genotyping with 90K wheat Infinium iSelect SNP arrays. Qfhb.ndwp-2A explained 14, 15, and 9% of the phenotypic variation, respectively, for FHB severity in two greenhouse experiments and for mean DON content across the two greenhouse environments. Qfhb.ndwp-5A explained 19, 10, and 7% of phenotypic variation, respectively, for FHB severity in one greenhouse experiment, mean FHB severity across two field experiments, and mean DON content across the two greenhouse experiments. Qfhb.ndwp-7A was only detected for FHB severity in the two greenhouse experiments, explaining 9 and 11% of the phenotypic variation, respectively. This study confirms the existence of minor QTL in North Dakota durum cultivars and the successful transfer of the major QTL from PI 277012 into durum wheat.

     

QTL analysis of resistance to Fusarium head blight in the novel wheat germplasm CJ 9306. I. Resistance to fungal spread

Fusarium head blight (FHB or scab) caused by Fusarium species is a destructive disease in wheat and barley worldwide. The objectives of our study were to identify quantitative trait loci (QTLs) for resistance to FHB spread (Type II resistance) and to quantify the magnitude of their effects in a novel highly resistant wheat germplasm, CJ 9306. A set of 152 F₇ recombinant inbred lines (RILs) derived from a cross Veery/CJ 9306 and two parents were evaluated for FHB resistance by single-floret inoculation in three greenhouse experiments in 2002 and 2004. Percentage (PSS) and number (NSS) of scabby spikelets at 25 days post-inoculation were analyzed. In total 682 simple sequence repeat (SSR) markers were screened for polymorphism between the two parents, and a genetic linkage map was constructed with 208 polymorphic markers. Ten QTLs associated with FHB resistance were detected, five from CJ 9306 and five from Veery. The major QTL on 3BS (QFhs.ndsu–3BS) was validated in CJ 9306, exhibiting greatest additive effects and explained 30.7% of phenotypic variation for PSS on the overall average of three experiments. Another major QTL on 2DL (QFhs.nau–2DL) from CJ 9306 explained 9.9–28.4% of phenotypic variation, with a significant QTL × environment interaction. QFhs.nau–1AS and QFhs.nau-7BS showed lower additive effects and explained lower variance (4.5–9.5%). A QTL on 5AS, decreasing PSS by 10.3% on average, was validated by simple marker analysis and joint trait/experiment IM/CIM analysis despite insignificance for single-experiment IM and CIM analyses. Likewise, QFhs.nau-2BL and QFhs.nau-1BC from Veery could reduce PSS by 13.2 and 11.4%, respectively. The effects of other three minor QTLs from Veery were significant for one experiment and combined analysis. Comparisons of two- and three-locus combinations suggested that the effects of FHB resistance QTLs/genes could be accumulated, and the resistance could be feasibly enhanced by selection of favorable alleles for multiple loci. Four two-locus combinations and two three-locus combinations were suggested as the preferential choices in practical marker-assisted selection program.     

Molecular mapping of Fusarium head blight resistance in the winter wheat population Dream/Lynx

Fusarium head blight (FHB), mainly caused by Fusarium graminearum and F. culmorum, can significantly reduce the grain quality of wheat (Triticum aestivum L.) due to mycotoxin contamination. The objective of this study was to identify quantitative trait loci (QTLs) for FHB resistance in a winter wheat population developed by crossing the resistant German cultivar Dream with the susceptible British cultivar Lynx. A total of 145 recombinant inbred lines (RILs) were evaluated following spray inoculation with a F. culmorum suspension in field trials in 2002 in four environments across Germany. Based on amplified fragment length polymorphism and simple sequence repeat marker data, a 1,734 cM linkage map was established assuming that the majority of the polymorphic parts of the genome were covered. The area under disease progress curve (AUDPC) was calculated based on the visually scored FHB symptoms. The population segregated quantitatively for FHB severity. Composite interval mapping analysis for means across the environments identified four FHB resistance QTLs on chromosomes 6AL, 1B, 2BL and 7BS. Individually the QTLs explained 19%, 12%, 11% and 21% of the phenotypic variance, respectively, and together accounted for 41%. The QTL alleles conferring resistance on 6AL, 2BL and 7BS originated from cv. Dream. The resistance QTL on chromosome 6AL partly overlapped with a QTL for plant height. The FHB resistance QTL on 7BS coincided with a QTL for heading date, but the additive effect on heading date was of minor importance. The resistance QTL on chromosome 1B was associated with the T1BL.1RS wheat-rye translocation of Lynx.     

Detection of Fusarium head blight resistance QTL in a wheat population using bulked segregant analysis

A population of 218 recombinant inbred lines (RILs) was developed from the cross of two wheat (Triticum aestivum L.) cultivars, 'Ning 894037' and 'Alondra'. Ning 894037 has resistance to Fusarium head blight (FHB) and Alondra is moderately susceptible. Response of the RILs and their parental lines to FHB infection was evaluated with point inoculation in four experiments both in greenhouse and in field conditions. Distribution of disease severity in the population is continuous, indicating quantitative inheritance of resistance to FHB. Bulked segregant analysis and QTL mapping based on simple sequence repeat (SSR) markers revealed three chromosome regions that are responsible for FHB resistance. A chromosome region on 3BS accounted for 42.5% of the phenotypic variation for FHB resistance. Additional QTLs were located on chromosomes 2D and 6B. These three QTLs jointly accounted for 51.6% of the phenotypic variation. SSR markers linked to the QTLs influencing resistance to FHB have potential for use in breeding programs.     

Quantitative trait loci for resistance to pre-harvest sprouting in US hard white winter wheat Rio Blanco

Pre-harvest sprouting (PHS) of wheat is a major problem that severely limits the end-use quality of flour in many wheat-growing areas worldwide. To identify quantitative trait loci (QTLs) for PHS resistance, a population of 171 recombinant inbred lines (RILs) was developed from the cross between PHS-resistant white wheat cultivar Rio Blanco and PHS-susceptible white wheat breeding line NW97S186. The population was evaluated for PHS in three greenhouse experiments and one field experiment. After 1,430 pairs of simple sequence repeat (SSR) primers were screened between the two parents and two bulks, 112 polymorphic markers between two bulks were used to screen the RILs. One major QTL, QPhs.pseru-3AS, was identified in the distal region of chromosome 3AS and explained up to 41.0% of the total phenotypic variation in three greenhouse experiments. One minor QTL, QPhs.pseru-2B.1, was detected in the 2005 and 2006 experiments and for the means over the greenhouse experiments, and explained 5.0-6.4% of phenotypic variation. Another minor QTL, QPhs.pseru-2B.2, was detected in only one greenhouse experiment and explained 4.5% of phenotypic variation for PHS resistance. In another RIL population developed from the cross of Rio Blanco/NW97S078, QPhs.pseru-3AS was significant for all three greenhouse experiments and the means over all greenhouse experiments and explained up to 58.0% of phenotypic variation. Because Rio Blanco is a popular parent used in many hard winter wheat breeding programs, SSR markers linked to the QTLs have potential for use in high-throughput marker-assisted selection of wheat cultivars with improved PHS resistance as well as fine mapping and map-based cloning of the major QTL QPhs.pseru-3AS.     

Marker-assisted characterization of Asian wheat lines for resistance to Fusarium head blight

The major quantitative trait locus (QTL) on 3BS from Sumai 3 and its derivatives has been used as a major source of resistance to Fusarium head blight (FHB) worldwide, but resistance genes from other sources are necessary to avoid complete dependence on a single source of resistance. Fifty-nine Asian wheat landraces and cultivars differing in the levels of FHB resistance were evaluated for type II FHB resistance and for genetic diversity on the basis of amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSRs). Genetic relationships among these wheat accessions estimated by cluster analysis of molecular marker data were consistent with their geographic distribution and pedigrees. Chinese resistant landraces had broader genetic diversity than that of accessions from southwestern Japan. The haplotype pattern of the SSR markers that linked to FHB resistance quantitative trait loci (QTLs) on chromosomes 3BS, 5AS and 6BS of Sumai 3 suggested that only a few lines derived from Sumai 3 may carry all the putative QTLs from Sumai 3. About half of the accessions might have one or two FHB resistance QTLs from Sumai 3. Some accessions with a high level of resistance, may carry different FHB resistance loci or alleles from those in Sumai 3, and are worth further investigation. SSR data also clearly suggested that FHB resistance QTLs on 3BS, 5AS, and 6BS of Sumai 3 were derived from Chinese landrace Taiwan Xiaomai.     

Mapping of Fhb2 on chromosome 6BS: a gene controlling Fusarium head blight field resistance in bread wheat (Triticum aestivum L.)

Fusarium head blight (FHB) is one of the most important fungal wheat diseases worldwide. Understanding the genetics of FHB resistance is key to facilitate the introgression of different FHB resistance genes into adapted wheat. The objective of this project was to study the FHB resistance QTL on chromosome 6B, quantify the phenotypic variation, and qualitatively map the resistance gene as a Mendelian factor. The FHB resistant parent BW278 (AC Domain*2/Sumai 3) was used as the source of the resistance allele. A large recombinant inbred line (RIL) mapping population was developed from the cross BW278/AC Foremost. The population segregated for three known FHB resistance QTL located on chromosomes 3BSc, 5A, and 6B. Molecular markers on chromosome 6B (WMC104, WMC397, GWM219), 5A (GWM154, GWM304, WMC415), and 3BS (WMC78, GWM566, WMC527) were amplified on approximately 1,440 F_2:7 RILs. The marker information was used to select 89 RILs that were fixed homozygous susceptible for the 3BSc and 5A FHB QTLs and were recombinant in the 6B interval. Disease response was evaluated on 89 RILs and parental checks in the greenhouse and field nurseries. Dual floret injection (DFI) was used in greenhouse trials to evaluate disease severity (DS). Macroconidial spray inoculations were used in field nurseries conducted at two locations in southern Manitoba (Carman and Glenlea) over two years 2003 and 2004, to evaluate disease incidence, disease severity, visual rating index, and Fusarium-damaged kernels. The phenotypic distribution for all five-disease infection measurements was bimodal, with lines resembling either the resistant or susceptible checks and parents. All of the four field traits for FHB resistance mapped qualitatively to a coincident position on chromosome 6BS, flanked by GWM133 and GWM644, and is named Fhb2. The greenhouse-DS trait mapped 2 cM distal to Fhb2. Qualitative mapping of Fhb2 in wheat provides tightly linked markers that can reduce linkage drag associated with marker assisted selection of Fhb2 and aid the pyramiding of different resistance loci for wheat improvement.     

Mapping of FHB resistance QTLs in tetraploid wheat.

Triticum turgidum L var. durum is known to be particularly susceptible to infection by Fusarium graminearum, the causal agent for Fusarium head blight (FHB), which results in severe yield losses and grain contaminated with mycotoxins. This research was aimed at identifying FHB resistance in tetraploid wheat and mapping the location of FHB resistance genes. A tetraploid cross of durum wheat ('Strongfield') x Triticum carthlicum ('Blackbird') was used to generate a doubled-haploid (DH) population. This population was evaluated for type II resistance to F. graminearum in replicated greenhouse trials, in which heads were innoculated and the percent of infected spikelets was determined 21 days later. The population was also genotyped with microsatellite markers to construct a map of 424 loci, covering 2 052 cM. The FHB reaction and genotypic data were used to identify FHB resistance quantitative trait loci (QTLs). It was determined that 2 intervals on chromosomes 2BL and 6BS controlled FHB resistance in this tetraploid cross. The FHB resistance allele on chromosome 2BL (r2=0.26, logarithm of odds (LOD)=8.5) was derived from 'Strongfield', and the FHB resistance allele on chromosome 6BS (r2=0.23, LOD=6.6) was derived from 'Blackbird'. Two other loci, on chromosomes 5AS and 2AL, were shown to regulate FHB infection and to have an epistatic effect on the FHB resistance QTL on chromosome 6BS. Further, the FHB resistance QTL peak on chromosome 6BS was clearly coincident with the known FHB resistance gene Fhb2, derived from Sumai 3. The results show that FHB resistance can be expressed in durum wheat, and that T. carthlicum and Triticum aestivum likely share a common FHB resistance gene on chromosome 6BS.     

Evaluation of genetic diversity of Fusarium head blight resistance in European winter wheat

Genetic diversity in relation to Fusarium head blight (FHB) resistance was investigated among 295 European winter wheat cultivars and advanced breeding lines using 47 wheat SSR markers. Twelve additional wheat lines with known FHB resistance were included as reference material. At least one SSR marker per chromosome arm, including SSR markers reported in the literature with putative associations with QTLs for FHB resistance, were assayed to give an even distribution of SSR markers across the wheat genome. A total of 404 SSR alleles were detected. The number of alleles per locus ranged from 2 to 21, with an average of 8.6 alleles. The polymorphism information content of the SSR markers ranged from 0.13 (Xwmc483) to 0.87 (Xwmc607), with an average of 0.54. Cluster analysis was performed by both genetic distance-based and model-based methods. In general, the dendrogram based on unweighted pair-group method with arithmetic averages showed similar groupings to the model-based analysis. Seven clusters were identified by the model-based method, which did not strictly correspond to geographical origin. The FHB resistance level of the wheat lines was evaluated in field trials conducted over multiple years or locations by assessing the following traits: % FHB severity, % FHB incidence, % diseased kernels, in spray inoculation trials, and % FHB spread and % wilted tips, in point inoculation trials. Association analysis between SSR markers and the FHB disease traits detected markers significantly associated with FHB resistance, including some that have not been previously reported. The percentage of variance explained by each individual marker was, however, rather low. Haplotype analysis revealed that the FHB-resistant European wheat lines do not contain the 3BS locus derived from Sumai 3. The information generated in this study will assist in the selection of parental lines in order to increase the efficiency of breeding efforts for FHB resistance.     

A novel quantitative trait locus for Fusarium head blight resistance in chromosome 7A of wheat

A Chinese Spring-Sumai 3 chromosome 7A disomic substitution line (CS-Sumai 3-7ADSL) was reported to have a high level of Fusarium head blight (FHB) resistance for symptom spread within a spike (Type II) and low deoxynivalenol accumulation in infected kernels (Type III), but a quantitative trait locus (QTL) on chromosome 7A has never been identified from this source. To characterize QTL on chromosome 7A, we developed 191 7A chromosome recombinant inbred lines (7ACRIL) from a cross between Chinese Spring and CS-Sumai 3-7ADSL and evaluated both types of resistance in three greenhouse experiments. Two major QTL with Sumai 3 origin, conditioning both Type II and III resistance, were mapped in the short arm of chromosomes 3B (3BS) and near the centromere of chromosome 7A (7AC). The 3BS QTL corresponds to previously reported Fhb1 from Sumai 3, whereas 7AC QTL, designated as Fhb7AC, is a novel QTL identified from CS-Sumai 3-7ADSL in this study. Fhb7AC explains 22% phenotypic variation for Type II and 24% for Type III resistance. Marker Xwmc17 is the closest marker to Fhb7AC for both types of resistance. Fhb1 and Fhb7AC were additive, and together explained 56% variation for Type II and 41% for Type III resistance and resulted in 66% reduction in FHB severity and 84% reduction in deoxynivalenol (DON) content. Haplotype analysis of Sumai 3 parents revealed that Fhb7AC originated from Funo, an Italian cultivar. Fhb7AC has the potential to be used in improving wheat cultivars for both types of resistance.     

DNA marker analysis for pyramided of Fusarium head blight (FHB) resistance QTLs from different germplasm

A pyramided FHB resistance line of wheat (WSY) was previously developed from three FHB resistant cultivars (Sumai 3, Wangshuibai, and Nobeokabouzu) in the Jiangsu Academy of Agricultural Sciences, China. In the present study, we analyzed the genetic relationship between WSY and the three parental cultivars using DNA markers in order to clarify how many and which resistance genes had accumulated in WSY. We analyzed 282 DNA markers from the 21 wheat chromosomes. WSY was found to include different chromosome regions that harbored putative FHB QTLs of the three parental germplasm. Haplotypes of DNA markers on these QTL regions revealed that the 1BL, 2BL, 5AS, and 7AL QTL regions were from Sumai 3, the 2AS, 2DS, 3AS, and 6BS QTL regions were from Wangshuibai, and the 3BS QTL region was from Nobeokabouzu. This study showed that different resistance genes from the different resistant germplasm had indeed accumulated in WSY. WSY is a potential resistant resource for FHB resistance in wheat breeding programs.     

QTL mapping of adult-plant resistance to leaf rust in a RIL population derived from a cross of wheat cultivars Shanghai 3/Catbird and Naxos

Key message

Six QTL for adult plant resistance to leaf rust, including two QTL effective against additional diseases, were identified in a RIL population derived from a cross between Shanghai 3/Catbird and Naxos.

Abstract

Leaf rust is an important wheat disease and utilization of adult-plant resistance (APR) may be the best approach to achieve long-term protection from the disease. The CIMMYT spring wheat line Shanghai 3/Catbird (SHA3/CBRD) showed a high level of APR to Chinese Puccinia triticina pathotypes in the field. To identify APR genes in this line, a mapping population of 164 recombinant inbred lines (RILs) was developed from a cross of this line and Naxos, a moderately susceptible German cultivar. The RILs were evaluated for final disease severity (FDS) at Baoding, Hebei province, and Zhoukou, Henan province, in the 2010–2011 and 2011–2012 cropping seasons. QTL analysis detected one major QTL derived from SHA3/CBRD on chromosome 2BS explaining from 15 to 37 % of the phenotypic variance across environments. In addition one minor resistance QTL on chromosome 1AL from SHA3/CBRD and four minor QTL from Naxos on chromosomes 2DL, 5B, 7BS, and 7DS were also detected. SHA3/CBRD also possessed seedling resistance gene Lr26, and Naxos contained Lr1 based on gene postulation following tests with an array of P. triticina pathotypes and molecular marker assays. These seedling resistance and APR genes and their closely linked molecular markers are potentially useful for improving leaf rust resistance in wheat breeding programs.     

QTL mapping of Fusarium head blight resistance in three related durum wheat populations

Key message

The QTL Fhb1 was successfully introgressed and validated in three durum wheat populations. The novel germplasm and the QTL detected will support improvement of Fusarium resistance in durum wheat.

Abstract

Durum wheat (Triticum durum Desf.) is particularly susceptible to Fusarium head blight (FHB) and breeding for resistance is hampered by limited genetic variation within this species. To date, resistant sources are mainly available in a few wild relative tetraploid wheat accessions. In this study, the effect of the well-known hexaploid wheat (Triticum aestivum L.) quantitative trait locus (QTL) Fhb1 was assessed for the first time in durum wheat. Three F7-RIL mapping populations of about 100 lines were developed from crosses between the durum wheat experimental line DBC-480, which carries an Fhb1 introgression from Sumai-3, and the European T. durum cultivars Karur, Durobonus and SZD1029K. The RILs were evaluated in field experiments for FHB resistance in three seasons using spray inoculation and genotyped with SSR as well as genotyping-by-sequencing markers. QTL associated with FHB resistance were identified on chromosome arms 2BL, 3BS, 4AL, 4BS, 5AL and 6AS at which the resistant parent DBC-480 contributed the positive alleles. The QTL on 3BS was detected in all three populations centered at the Fhb1 interval. The Rht-B1 locus governing plant height was found to have a strong effect in modulating FHB severity in all populations. The negative effect of the semi-dwarf allele Rht-B1b on FHB resistance was compensated by combining with Fhb1 and additional resistance QTL. The successful deployment of Fhb1 in T. durum was further substantiated by assessing type 2 resistance in one population. The efficient introgression of Fhb1 represents a significant step forward for enhancing FHB resistance in durum wheat.

     

Combination of all-stage and high-temperature adult-plant resistance QTL confers high-level,durable resistance to stripe rust in winter wheat cultivar Madsen

Key message

Wheat cultivar Madsen has a new gene on the short arm of chromosome 1A and two QTL for all-stage resistance and three QTL for high-temperature adult-plant resistance that in combination confer high-level, durable resistance to stripe rust.

Abstract

Wheat cultivar Madsen has maintained a high-level resistance to stripe rust over 30 years. To map quantitative trait loci (QTL) underlying the high-level, durable resistance, 156 recombinant inbred lines (RILs) developed from cross Avocet S?×?Madsen were phenotyped with selected races of Puccinia striiformis f. sp. tritici in the greenhouse seedling tests, and in naturally infected fields during 2015–2017. The RILs were genotyped by SSR and SNP markers from genotyping by sequencing and the 90 K wheat SNP chip. Three QTL for all-stage resistance were mapped on chromosomes 1AS, 1BS and 2AS, and two QTL for high-temperature adult-plant (HTAP) resistance were mapped on 3BS and 6BS. The most effective QTL on 2AS, explaining 8.97–23.10% of the phenotypic variation in seedling tests and 8.60–71.23% in field tests, contained Yr17 for all-stage resistance and an additional gene for HTAP resistance. The 6BS QTL, detected in all field tests, was identified as Yr78. The 1AS QTL, conferring all-stage resistance, was identified as a new gene, which explained 20.45 and 30.23% of variation in resistance to races PSTv-37 and PSTv-40, respectively, and contributed significantly to field resistance at Pullman in 2015-2017, but was not detected at Mount Vernon. The interactions among QTL were mostly additive, and RILs with all five QTL had the highest level of resistance in the field, similar to Madsen. Genotyping 148 US Pacific Northwest wheat cultivars with markers for the 1AS, 2AS and 6BS QTL validated the genes and markers, and indicated their usefulness for marker-assisted selection.