Sources Of Fusarium Head Blight Resistance Research Articles

Identification of Fusarium head blight sources of resistance and associated QTLs in historical and modern Canadian spring wheat.

Fusarium head blight (FHB) is one the most globally destructive fungal diseases in wheat and other small grains, causing a reduction in grain yield by 10-70%. The present study was conducted in a panel of historical and modern Canadian spring wheat (Triticum aestivum L.) varieties and lines to identify new sources of FHB resistance and map associated quantitative trait loci (QTLs). We evaluated 249 varieties and lines for reaction to disease incidence, severity, and visual rating index (VRI) in seven environments by artificially spraying a mixture of four Fusarium graminearum isolates. A subset of 198 them were genotyped with the Wheat 90K iSelect single nucleotide polymorphisms (SNPs) array. Genome-wide association mapping performed on the overall best linear unbiased estimators (BLUE) computed from all seven environments and the International Wheat Genome Sequencing Consortium (IWGSC) RefSeq v2.0 physical map of 26,449 polymorphic SNPs out of the 90K identified sixteen FHB resistance QTLs that individually accounted for 5.7-10.2% of the phenotypic variance. The positions of two of the FHB resistance QTLs overlapped with plant height and flowering time QTLs. Four of the QTLs (QFhb.dms-3B.1, QFhb.dms-5A.5, QFhb.dms-5A.7, and QFhb.dms-6A.4) were simultaneously associated with disease incidence, severity, and VRI, which accounted for 27.0-33.2% of the total phenotypic variance in the combined environments. Three of the QTLs (QFhb.dms-2A.2, QFhb.dms-2D.2, and QFhb.dms-5B.8) were associated with both incidence and VRI and accounted for 20.5-22.1% of the total phenotypic variance. In comparison with the VRI of the checks, we identified four highly resistant and thirty-three moderately resistant lines and varieties. The new FHB sources of resistance and the physical map of the associated QTLs would provide wheat breeders valuable information towards their efforts in developing improved varieties in western Canada.

Identification of fusarium head blight resistance markers in a genome-wide association study of CIMMYT spring synthetic hexaploid derived wheat lines

Fusarium head blight (FHB), caused by Fusarium graminearum, is one of the most destructive wheat diseases worldwide. FHB infection can dramatically reduce grain yield and quality due to mycotoxins contamination. Wheat resistance to FHB is quantitatively inherited and many low-effect quantitative trait loci (QTL) have been mapped in the wheat genome. Synthetic hexaploid wheat (SHW) represents a novel source of FHB resistance derived from Aegilops tauschii and Triticum turgidum that can be transferred into common wheat (T. aestivum). In this study, a panel of 194 spring Synthetic Hexaploid Derived Wheat (SHDW) lines from the International Maize and Wheat Improvement Center (CIMMYT) was evaluated for FHB response under field conditions over three years (2017–2019). A significant phenotypic variation was found for disease incidence, severity, index, number of Fusarium Damaged Kernels (FDKs), and deoxynivalenol (DON) content. Further, 11 accessions displayed < 10 ppm DON in 2017 and 2019. Genotyping of the SHDW panel using a 90 K Single Nucleotide Polymorphism (SNP) chip array revealed 31 K polymorphic SNPs with a minor allele frequency (MAF) > 5%, which were used for a Genome-Wide Association Study (GWAS) of FHB resistance. A total of 52 significant marker-trait associations for FHB resistance were identified. These included 5 for DON content, 13 for the percentage of FDKs, 11 for the FHB index, 3 for disease incidence, and 20 for disease severity. A survey of genes associated with the markers identified 395 candidate genes that may be involved in FHB resistance. Collectively, our results strongly support the view that utilization of synthetic hexaploid wheat in wheat breeding would enhance diversity and introduce new sources of resistance against FHB into the common wheat gene pool. Further, validated SNP markers associated with FHB resistance may facilitate the screening of wheat populations for FHB resistance.

Screening of an Ethyl Methane Sulfonate Mutagenized Population of a Wheat Cultivar Susceptible to Fusarium Head Blight Identifies Resistant Variants.

Fusarium head blight (FHB) primarily caused by Fusarium graminearum is a key disease of small grains. Diseased spikes show symptoms of premature bleaching shortly after infection and have aborted or shriveled seeds, resulting in reduced yields. The fungus also deteriorates quality and safety of the grain because of production of mycotoxins, especially deoxynivalenol (DON), which can result in grain being docked or rejected at the point of sale. Genetic host resistance to FHB is quantitative, and no complete genetic resistance against this devastating disease is available. Alternative approaches to develop new sources of FHB resistance are needed. In this study, we performed extensive forward genetic screening of the M4 generation of an ethyl methane sulfonate-induced mutagenized population of cultivar Jagger to isolate variants with FHB resistance. In field testing, 74 mutant lines were found to have resistance against FHB spread, and 30 of these lines also had low DON content. Subsequent testing over 2 years in controlled greenhouse conditions revealed 10 M6 lines showing significantly lower FHB spread. Seven and 6 of those 10 lines also had reduced DON content and fewer Fusarium-damaged kernels, respectively. Future endeavors will include identification of the mutations that led to resistance in these variants.

Molecular cytogenetic characterization and fusarium head blight resistance of five wheat-Thinopyrum intermedium partial amphiploids

BackgroundPartial amphiploids created by crossing octoploid tritelytrigia(2n = 8× = 56, AABBDDEE) and Thinopyrum intermedium (2n = 6× = 42, StStJJJSJS) are important intermediates in wheat breeding because of their resistance to major wheat diseases. We examined the chromosome compositions of five wheat-Th. intermedium partial amphiploids using GISH and multicolor-FISH.ResultsThe result revealed that five lines had 10-14 J-genome chromosomes from Th. intermedium and 42 common wheat chromosomes, using the J-genomic DNA from Th. bessarabicum as GISH probe and the oligo probes pAs1-1, pAs1-3, AFA-4, (GAA) 10, and pSc119.2-1 as FISH probe. Five lines resembled their parent octoploid tritelytrigia (2n = 8× = 56, AABBDDEE) but had higher protein contents. Protein contents of two lines HS2-2 and HS2-5 were up to more than 20%. Evaluation of Fusarium head blight (FHB) resistance revealed that the percent of symptomatic spikelets (PSS) of these lines were below 30%. Lines HS2-2, HS2-4, HS2-5, and HS2-16 were less than 20% of PPS. Line HS2-5 with 14 J-genome chromosomes from Th. intermedium showed the best disease resistance, with PSS values of 10.8% and 16.6% in 2016 and 2017, respectively.ConclusionsNew wheat-Th. intermedium amphiploids with the J-genome chromosomes were identified and can be considered as a valuable source of FHB resistance in wheat breeding.

Searching for FHB Resistances in Bread Wheat: Susceptibility at the Crossroad.

Fusarium head blight (FHB), primarily caused by Fusarium graminearum, is one of the most devastating fungal wheat diseases. During the past decades, many efforts have been deployed to dissect FHB resistance, investigating both the wheat responses to infection and, more recently, the fungal determinants of pathogenicity. Although no total resistance has been identified so far, they demonstrated that some plant functions and the expression of specific genes are needed to promote FHB. Associated with the increasing list of F. graminearum effectors able to divert plant molecular processes, this fact strongly argues for a functional link between susceptibility-related factors and the fate of this disease in wheat. In this review, we gather more recent data concerning the involvement of plant and fungal genes and the functions and mechanisms in the development of FHB susceptibility, and we discuss the possibility to use them to diversify the current sources of FHB resistance.

Harnessing Wheat Fhb1 for Fusarium Resistance.

Fusarium head blight (FHB), caused by the fungus Fusarium graminearum, is an economically devastating disease of wheat worldwide. Fhb1, a widely used genetic source of FHB resistance, originated in East Asia. The recent cloning of Fhb1 opens a new avenue to improve FHB resistance in wheat and potentially other crops.

Fusarium Head Blight in Durum Wheat: Recent Status, Breeding Directions, and Future Research Prospects.

Fusarium head blight (FHB) is a major fungal disease affecting wheat production worldwide. Since the early 1990s, FHB, caused primarily by Fusarium graminearum, has become one of the most significant diseases faced by wheat producers in Canada and the United States. The increasing FHB problem is likely due to the increased adoption of conservation tillage practices, expansion of maize production, use of susceptible wheat varieties in rotation, and climate variability. Durum wheat (Triticum turgidum sp. durum) is notorious for its extreme susceptibility to FHB and breeding for resistance is complicated because sources of FHB resistance are rare in the primary gene pool of tetraploid wheat. Losses due to this disease include yield, test weight, seed quality, food and feed quality, and when severe, market access. More importantly, it is the contamination with mycotoxins, such as deoxynivalenol, in Fusarium-infected durum kernels that causes the most serious economic as well as food and feed safety concerns. Several studies and thorough reviews have been published on germplasm development and breeding for FHB resistance and the genetics and genomics of FHB resistance in bread or common wheat (T. aestivum); however, similar reviews have not been conducted in durum wheat. Thus, the aim of this review is to summarize and discuss the recent research efforts to mitigate FHB in durum wheat, including quantitative trait locus mapping, genome-wide association studies, genomic prediction, mutagenesis and characterization of genes and pathways involved in FHB resistance. It also highlights future directions, FHB-resistant germplasm, and the potential role of morphological traits to enhance FHB resistance in durum wheat.

Genetic Analysis of Fusarium Head Blight Resistance in CIMMYT Bread Wheat Line C615 Using Traditional and Conditional QTL Mapping.

Fusarium head blight (FHB) is a destructive wheat disease present throughout the world, and host resistance is an effective and economical strategy used to control FHB. Lack of adequate resistance resource is still a main bottleneck for FHB genetics and wheat breeding research. The synthetic-derived bread wheat line C615, which does not carry the Fhb1 gene, is a promising source of FHB resistance for breeding. A population of 198 recombinant inbred lines (RILs) produced by crossing C615 with the susceptible cultivar Yangmai 13 was evaluated for FHB response using point and spray inoculations. As the disease phenotype is frequently complicated by other agronomic traits, we used both traditional and multivariate conditional QTL mapping approaches to investigate the genetic relationships (at the individual QTL level) between FHB resistance and plant height (PH), spike compactness (SC), and days to flowering (FD). A linkage map was constructed from 3,901 polymorphic SNP markers, which covered 2,549.2 cM. Traditional and conditional QTL mapping analyses found 13 and 22 QTL for FHB, respectively; 10 were identified by both methods. Among these 10, three QTL from C615 were detected in multiple years; these QTL were located on chromosomes 2AL, 2DS, and 2DL. Conditional QTL mapping analysis indicated that, at the QTL level, SC strongly influenced FHB in point inoculation; whereas PH and SC contributed more to FHB than did FD in spray inoculation. The three stable QTL (QFhbs-jaas.2AL, QFhbp-jaas.2DS, and QFhbp-jaas.2DL) for FHB were partly affected by or were independent of the three agronomic traits. The QTL detected in this study improve our understanding of the genetic relationships between FHB response and related traits at the QTL level and provide useful information for marker-assisted selection for the improvement of FHB resistance in breeding.

Single Nucleotide Polymorphisms in B-Genome Specific UDP-Glucosyl Transferases Associated with Fusarium Head Blight Resistance and Reduced Deoxynivalenol Accumulation in Wheat Grain.

An in vitro spike culture method was optimized to evaluate Fusarium head blight (FHB) resistance in wheat (Triticum aestivum) and used to screen a population of ethyl methane sulfonate treated spike culture-derived variants (SCDV). Of the 134 SCDV evaluated, the disease severity score of 47 of the variants was ≤30%. Single nucleotide polymorphisms (SNP) in the UDP-glucosyltransferase (UGT) genes, TaUGT-2B, TaUGT-3B, and TaUGT-EST, differed between AC Nanda (an FHB-susceptible wheat variety) and Sumai-3 (an FHB-resistant wheat cultivar). SNP at 450 and 1,558 bp from the translation initiation site in TaUGT-2B and TaUGT-3B, respectively were negatively correlated with FHB severity in the SCDV population, whereas the SNP in TaUGT-EST was not associated with FHB severity. Fusarium graminearum strain M7-07-1 induced early expression of TaUGT-2B and TaUGT-3B in FHB-resistant SCDV lines, which were associated with deoxynivalenol accumulation and reduced FHB disease progression. At 8 days after inoculation, deoxynivalenol concentration varied from 767 ppm in FHB-resistant variants to 2,576 ppm in FHB-susceptible variants. The FHB-resistant SCDV identified can be used as new sources of FHB resistance in wheat improvement programs.

Validation of Molecular Markers for Use With Adapted Sources of Fusarium Head Blight Resistance in Wheat.

Genetic control of resistance to Fusarium head blight (FHB) is quantitative, making phenotypic selection difficult. Genetic markers to resistance are helpful to select favorable genotypes. This study was conducted to determine if Fhb1 and Fhb5 present in the Sumai 3 source of FHB resistance occur in Sumai 3-derived North American spring wheat cultivars and to understand the appropriateness of using markers to select for the favorable alleles at these loci in breeding. Sumai 3-derived parents Alsen, ND3085, ND744, Carberry, and Glenn were used in crosses to generate 14 doubled haploid breeding populations. The parents and progeny were genotyped with five Fhb1 and three Fhb5 microsatellite markers. Progeny were selected based on performance relative to parents and other control cultivars in FHB nurseries near Portage la Prairie and Carman, MB. χ2 and t test analyses were performed on marker and FHB data. The χ2 test frequently determined the proportion of lines carrying molecular variants associated with FHB resistance increased following nursery selection for FHB. Similarly, the t test regularly demonstrated that selection for FHB resistance lowered the mean level of disease associated with resistant marker haplotypes. The study affirmed FHB resistance sources Alsen, Carberry, ND3085, and ND744 have Fhb1 and Fhb5 loci like Sumai 3, but no evidence was found that Glenn carries Fhb1 and Fhb5 resistance alleles. The results justified use of Fhb1 and Fhb5 markers for marker assisted selection in populations derived from Alsen, Carberry, ND3085, and ND744, but not Glenn. Combined or individual application of Xgwm493 and Xgwm533 in selection of genotypes carrying Fhb1, and Xgwm150, Xgwm304, and Xgwm595 for Fhb5 will enhance FHB resistance in wheat.

Identification and molecular mapping of quantitative trait loci for Fusarium head blight resistance in emmer and durum wheat using a single nucleotide polymorphism-based linkage map

Fusarium head blight (FHB), caused by Fusarium graminearum, threatens durum wheat (Triticum turgidum subsp. durum) production in many durum-growing regions. It is critical to identify useful sources of FHB resistance for durum wheat. A domesticated emmer wheat (T. turgidum subsp. dicoccum) accession, PI 41025, was previously shown to be moderately resistant to FHB. This study aimed to identify quantitative trait loci (QTL) associated with FHB resistance in PI 41025. A population of 200 recombinant inbred lines were developed from a cross between the durum cultivar ‘Ben’ and PI 41025 and evaluated for reactions to F. graminearum in one field nursery and three greenhouse experiments. The disease severity data and a single nucleotide polymorphism marker-based linkage map from this population were used for QTL analysis. The results showed that one QTL on chromosome 2A from Ben and one QTL each on 3A and 5A from PI 41025 were associated with FHB resistance. The 2A and 3A QTL each explaining 8 % of the phenotypic variation were detected only in the greenhouse experiments. The QTL on 5A, which mapped near the domestication gene Q, explained 11 and 35 % of phenotypic variation in greenhouse and field evaluations, respectively. The identification of the 2A QTL from Ben confirmed the presence of FHB resistance in North Dakota durum cultivars, which have been successfully used for developing new cultivars with improved FHB tolerance. This study indicates that combining the QTL from related tetraploid species with native durum QTL will be useful for improving FHB resistance in durum.

Durum wheat genetic stocks involving chromosome 1E of diploid wheatgrass: resistance to Fusarium head blight

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) is the preferred wheat for preparing pasta products. Current durum cultivars have little resistance to Fusarium head blight (FHB), or scab, a ravaging fungal disease. In our Durum Germplasm Enhancement (DGE) project, we previously showed that chromosome 1E of diploid wheatgrass Lophopyrum elongatum (Host) A. Love (2n = 2x = 14; EE genome) is an excellent source of FHB resistance. Through hybridization of this grass with the durum cultivar Langdon, coupled with manipulation of chromosome pairing and selection, we added the chromosome 1E pair into the durum genome and produced a fertile durum 1E addition line, called DGE-1. Also by substituting 1E for the durum homoeologues 1A or 1B, we produced, two fertile disomic substitution lines, 1E(1A) and 1E(1B), which were designated as DGE-2 and DGE-3, respectively. The level of FHB resistance of the genetic stocks was studied in the greenhouse and in the field at Prosper, North Dakota. In the greenhouse, the 1E addition showed 32.15 % infection and was better than Langdon at 58.73 %, but not significantly different from 1E(1A) disomic substitution at 45.60 % infection. The 1E(1B) disomic substitution (88.29 % infection) had the highest FHB infection. Under natural conditions in the field, the observed infection rates were essentially similar. Among the three genetic stocks, the 1E addition DGE-1 had the lowest level of infection (at 10 %) followed by the substitution 1E(1A) at 20 %, and the substitution E(1B) at 70 %. The parental cultivar Langdon had 15 % FHB infection. The genetic stocks of durum may help produce several more alien addition and substitution lines involving different chromosomes and may help locate sources of FHB resistance.

Identification of novel QTL for resistance to Fusarium head blight in a tetraploid wheat population

Most tetraploid durum wheat (Triticum turgidum L var. durum) cultivars are susceptible to Fusarium head blight (FHB). This study reports novel quantitative trait loci (QTL) associated with FHB resistance. A backcross recombinant inbred line (BCRIL) population was developed from the cross BGRC3487/2*DT735, and 160 lines were evaluated for resistance to Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schwein. Petch) in field trials over 3 years (2008-2010) and to a F. graminearum 3-acetyl-deoxynivalenol (3-ADON) chemotype in greenhouse trials. The population was genotyped with 948 polymorphic loci using DArT and microsatellite markers. Eleven QTL were associated with FHB resistance under field conditions on chromosomes 2A, 3B, 5A, 5B, 7A, and 7B. Two of these, QFhb.usw-3B from BGRC3487 and QFhb.usw-7A2, were consistently detected over environments. The QFhb.usw-3B QTL was in a similar position to a resistance QTL in hexaploid wheat. The combination of the two QTL reduced field index by 53.5%-86.2%. Two QTL for resistance to the 3-ADON chemotype were detected on chromosomes 1B and 4B. Both BGRC3487 and DT735 could provide new sources of FHB resistance and the combination of QTL reported here could be valuable tools in breeding FHB-resistant durum wheat.

Molecular Characterization of Resistance to Fusarium Head Blight in U.S. Soft Red Winter Wheat Breeding Line VA00W‐38

ABSTRACTMany quantitative trait loci (QTL) in wheat (Triticum aestivum L.) conferring resistance to Fusarium head blight (FHB), caused by the Fusarium graminearium, have been mapped in diverse genetic sources. Use of nonadapted FHB resistant sources by breeding programs in the soft red winter (SRW) wheat region of the United States has not been very successful. Therefore, native sources of FHB resistance identified or validated in SRW wheat cultivars predominantly have been used. The breeding line VA00W‐38 has moderate FHB resistance and does not possess any previously identified exotic sources of resistance in its parentage. A set of 182 recombinant inbred lines (RILs) were developed from the cross VA00W‐38 × Pioneer brand ‘26R46’ and tested in field scab nurseries and natural conditions in two environments for each of 2 yr. Eight consistent QTL were identified on chromosomes 1BL, 2A, 2DL, 5B, 6A, and 7A and explained 6.5 to 21.3% of phenotypic variation of traits associated with FHB resistance. Their logarithm of odds (LOD) scores ranged from 2.5 to 6.7. Favorable alleles to decrease FHB are from VA00W‐38 except one QTL on chromosome 7A. Major QTL on chromosomes 2DL, 6A, and 5B decreased FHB index (IND), Fusarium damaged kernels (FDK), and deoxynivalenol (DON), respectively. Tightly linked markers identified for these consistent QTL can be used to select for favorable alleles associated with FHB resistance in breeding populations after validation in diverse genetic backgrounds.

Cytological and Molecular Characterization of Homoeologous Group-1 Chromosomes in Hybrid Derivatives of a Durum Disomic Alien Addition Line

Earlier, we produced a stable Fusarium head blight (FHB)-tolerant durum wheat (Triticum turgidum L.) alien disomic addition line, DGE-1 (released in 2008), incorporating chromosome 1E of diploid wheatgrass [Lophopyrum elongatum (Host) A. Love; 2n = 2x = 14; EE]. For stable FHB resistance, the ultimate goal would be to transfer resistance from 1E into the durum chromosome 1A or 1B. Such transfer is more likely to occur when these target chromosomes are in a single dose. Therefore, we crossed DGE-1 with ‘Langdon’ substitution lines 1D(1A) and 1D(1B) and produced hybrid derivatives with chromosomes 1A, 1B, 1D, and 1E in a single dose. As an important fi rst step, we standardized a method to readily identify these group-1 chromosomes. Multicolor fl uorescent genomic in situ hybridization that we standardized earlier is useful for such identifi cation but is tedious and expensive. To identify these chromosomes more expeditiously and economically in a large plant population, we also used chromosome-specifi c molecular markers and identifi ed each of the group-1 chromosomes. We used marker Xwmc333 to identify chromosome 1A, Xwgm18 for 1B, Xwmc147 for 1D, and Xedm17 for 1E. Xedm17, which profi les chromosome 1E, also generated two characteristic bands for chromosome 1D and may therefore be useful in identifying both chromosomes simultaneously. DURUM WHEAT (Triticum turgidum L.; 2n = 4x = 28; AABB) is an important cereal used for human consumption in the United States, Canada, and most European countries, including Italy, Turkey, France, Romania, and Ukraine. On the evolutionary ladder, durum wheat is a forerunner of bread wheat (Triticum aestivum L.; 2n = 6x = 42; AABBDD) and evolved in nature long before the latter (see Jauhar, 2006). Durum wheat is a natural hybrid, having resulted from hybridization between related wild species in conjunction with doubling of chromosome number. Th us, it enjoys the benefi ts of both polyploidy and hybridity. It has a unique cytogenetic architecture and its chromosomes can be divided into seven homoeologous groups of two chromosomes each (Fig. 1). Th e chromosomes within a homoeologous group are genetically and evolutionarily related. Durum wheat can tolerate addition of certain chromosomes, of related species, syntenic to those within a homoeologous group. A related species, diploid wheatgrass [Lophopyrum elongatum (Host) A. Love; 2n = 2x = 14; EE genome] is an excellent source of Fusarium head blight (FHB) resistance (Jauhar and Peterson, 1998). In our earlier work on durum germplasm enhancement (DGE), we produced a stable alien disomic addition line, DGE-1, incorporating chromosome 1E of L. elongatum (Jauhar and Peterson, 2008; Jauhar et al., 2009). DGE-1 is the fi rst alien addition line of its kind with a novel source of FHB resistance from chromosome 1E. Th e ultimate goal would be to transfer FHB resistance from the added alien chromosome 1E into the durum chromosome complement. Homoeologous group-1 chromosomes 1A and/or 1B of durum wheat would naturally be the logical Published in The Plant Genome 4:102–109. Published 21 June 2011. doi: 10.3835/plantgenome2011.01.0002 © Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA An open-access publication All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. USDA-ARS, Northern Crop Science Lab., Fargo, ND 58102. Mention of trade names or commercial products in this publication is solely to provide specifi c information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. Received 26 Aug. 2010. *Corresponding author (prem.

Chromosome Engineering of Durum Wheat with Alien Chromatin of Diploid Wheatgrass

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) is an important cereal widely used for human consumption. It is the choice wheat for preparing pasta products. Current durum cultivars have little resistance to Fusarium head blight (FHB), or scab, a ravaging fungal disease caused by the fungal pathogen Fusarium graminearum Schwabe. We showed earlier that diploid wheatgrass (Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) is an excellent source of FHB resistance, which could be transferred to commercial durum cultivars by hybridization coupled with manipulation of chromosome pairing. We obtained homoeologous pairing (i.e., pairing between wheat and alien chromosomes) in intergeneric hybrids because of the wheatgrass-induced suppression of the pairing-regulating gene Ph1 of wheat, leading to alien chromatin integration into the durum genome. Adopting this chromosome engineering technology, we have transferred diploid wheatgrass chromatin into the durum genome. We have produced fertile hybrid derivatives with varying degrees of FHB resistance. Some derivatives showed only 7.6% infection compared with 72.0% in the parental durum cultivar. Fluorescent genomic in situ hybridization (fl-GISH) analysis was used to confirm the integration of alien chromatin into the durum complement.

Cereal resistance to Fusarium head blight and possibilities of its improvement through breeding

The aim of this review is to summarize recent information on Fusarium head blight (FHB) in small grain cereals, especially in wheat and barley. Basic information on FHB epidemiology, types of resistance and plant resistance mechanisms is included. Standard methods for the evaluation of the individual types of FHB resistance and the extent of infection are briefly described. Special attention is paid to the sources of FHB resistance of different origin and possibility of their exploitation in cereal breeding. Unfortunately, a high level of FHB resistance was detected in non-adapted germplasm or distant relatives, which is a serious impediment to breeding progress in this field. The present state of breeding for FHB resistance in wheat, barley, rye, triticale and oats was analyzed. It was shown that large-scale QTL detections provide new opportunities for increasing the resistance; however, multi-step phenotypic selection still remains to be the most effective tool. Pedigree analyses indicated that the latest progress reached in this field was obtained through the cumulation of resistance genes coming from heterogeneous sources with different response to FHB.

Identification of QTL Conferring Resistance to Fusarium Head Blight Resistance in the Breeding Line C93‐3230‐24

ABSTRACTControl of Fusarium head blight (FHB), incited primarily by Fusarium graminearum Schwabe [telomorph Gibberella zea (Schwein)], has been a challenge for barley (Hordeum vulgare L.) producers in the upper midwestern United States for more than a decade. This disease manifests primarily in the form of food safety issues and quality discounts due to the presence of deoxynivalenol (DON), a mycotoxin produced by the pathogen. Cultural practices and fungicides only provide partial control; genetic resistance to FHB and DON accumulation may add to control of the disease. Field studies in North Dakota and China were conducted in FHB disease nurseries using 118 double‐haploid lines from the cross C93‐3230‐24/‘Foster’. Foster is susceptible to FHB, and C93‐3230‐24 is moderately resistant. The quantitative trait locus (QTL) analysis revealed five putative QTL for Type I FHB resistance; however, only the one in bins 7 and 8 of chromosome 2H was detected in more than 70% of the environments. In addition, QTL associated with late days to heading and maturity and tall plant height also were located in the same region. Three putative QTL for increased DON accumulation were detected; however, none were detected in more than three of the eight environments where data were collected. On the basis of these results, it is unlikely that C93‐3230‐24 has a novel QTL for FHB resistance different from those identified in other resistant accessions. However, C93‐3230‐24 is unique in that it provides QTL for improved FHB resistance but not reduced DON accumulation. This is an atypical response compared with other sources of FHB resistance and provides evidence that FHB resistance and DON accumulation are under separate genetic control.

Cytogenetic and molecular characterization of a durum alien disomic addition line with enhanced tolerance to Fusarium head blight

Current durum wheat (Triticum turgidum L. subsp. durum (Desf.)) cultivars have little or no resistance to Fusarium head blight (FHB), a ravaging disease of cereal crops. A diploid wheatgrass, Lophopyrum elongatum (Host) A. Löve (2n = 2x = 14, EE genome), is an excellent source of FHB resistance. Through an extensive intergeneric hybridization using durum cultivar Langdon, we have developed a disomic alien addition line, named DGE-1 (2n = 28 + 2), with a wheatgrass chromosome pair. We used a unique method for isolating the addition line taking advantage of unreduced gametes functioning in Langdon x L. elongatum F1 hybrids in their first backcross to the Langdon parent, resulting in 35-chromosome plants from which we derived DGE-1. The addition line DGE-1 has a plant type similar to its Langdon parent, although it is shorter in height with narrower leaves and shorter spikes. It is meiotically and reproductively stable, generally forming 15 bivalents with two chiasmata each. The alien chromosome pair from the grass confers FHB resistance to the addition line, which has less than 21% infection on the visual scale, mean = 6.5%. Using various biochemical and molecular techniques (Giemsa C-banding, fluorescent genomic in situ hybridization (fl-GISH), chromosome-specific simple sequence repeat (SSR) markers, targeted region amplified polymorphism (TRAP) markers, and sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE)), we have shown that the extra chromosome involved is 1E of L. elongatum. This is the first time that FHB resistance has been discovered on chromosome 1E. We have established a chromosome-specific marker for 1E that may be used to screen fertile hybrid derivatives and durum addition lines for this chromosome that confers FHB resistance.

Quantitative Trait Loci Associated with Deoxynivalenol Content and Kernel Quality in the Soft Red Winter Wheat ‘Ernie’

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe [telomorph: Gibberella zeae (Schwein.) Petch] reduces quality in wheat (Triticum aestivum L.) when deoxynivalenol (DON) accumulates in the grain. ‘Ernie’ soft red winter wheat has been used as a source of FHB resistance in many U.S. breeding programs because of its type II resistance, low DON, and good kernel quality under heavy disease pressure. The objectives of this study were to identify quantitative trait loci (QTL) associated with both low DON and kernel quality and to determine their association with QTL previously identified for type II resistance in Ernie. Data for DON and Fusarium damaged kernels (FDK) were collected from 243 recombinant inbred lines of the cross Ernie/MO 94‐317 grown in inoculated greenhouse experiments conducted in 2002 and 2003. A total of 420 simple sequence repeat and 64 EcoRI/MseI amplified fragment length polymorphism primers were used for parental screening. Three QTL were consistently identified on chromosomes 3BSc, 4BL, and 5AS for both DON and FDK that explained 31 and 42% of the total phenotypic variation in these two traits, respectively. A fourth minor QTL on 2B (R2 = 4%) was also detected for FDK but was not significant for DON. These QTL were coincidental with those previously identified for type II resistance in Ernie, which suggested that the inheritance of these three resistance factors is interdependent in this variety. These findings should enhance the efficiency of using this source of resistance for FHB‐resistance breeding.