Hessian Fly Resistance Research Articles

Triticum monococcum subsp. monococcum and aegilopoides: new sources of resistance to the dipteran pest, Hessian fly (Diptera: Cecidomyiidae).

The Hessian fly, Mayetiola destructor (Say) belonging to the order Diptera (family: Cecidomyiidae), is a destructive pest of host wheat (Triticum aestivum L.) causing significant economic losses. Although planting resistant wheat cultivars harboring an effective Hessian fly resistance gene (H) is the most economical and environmentally friendly pest management strategy, it imposes selection pressure on the insect populations and can lead to the evolution of Hessian fly virulence. This results in the eventual failure of the deployed H gene. New sources and novel types of resistance are urgently needed to expand the repertoire of H genes and enable strategies that are more effective and durable over the long-term. New sources of Hessian fly resistance have been identified from tetraploid (T. turgidum L., AABB) and hexaploid (T. aestivum, AABBDD) wheat species, as well as from wheat's D-genome donor (Aegilops tauschii Coss., DD). In contrast, diploid einkorn wheat (T. monococcum L., AA) has not been extensively explored for Hessian fly resistance. In this study, we phenotyped 506 T. monococcum accessions belonging to 2 subspecies, T. monococcum L. subsp. monococcum (205 accessions) and T. monococcum subsp. aegilopoides (Link) Thell. (301 accessions), for resistance against 2 predominant Hessian fly biotypes, L and GP (Great Plains). Three and 6 accessions belonging to subsp. monococcum and aegilopoides, respectively, showed > 70% resistance. These accessions provide additional resources for improving wheat cultivars as mitigating strategies for Hessian fly management.

The Hessian fly resistance gene HvRHF1 is localized in an NBS-LRR gene cluster in barley.

Hessian fly (Mayetiola destructor Say) is a significant pest in cereal crops, causing substantial yield losses worldwide. While host resistance is the most efficient method for pest control, research on genetic characterization of Hessian fly resistance in barley (Hordeum vulgare L.) has been limited, and the underlying resistance mechanism remains largely unknown. In this study, we conducted fine mapping of a crucial Hessian fly resistance locus, known as HvRHF1, using a biparental population. Assisted with genetic markers and robust phenotyping assay, we pinpointed the HvRHF1 gene to an ~ 82kb region on chromosome 4H. Gene prediction and annotation revealed that the HvRHF1 locus comprises three complete NBS-LRR genes, which are characteristic of disease resistance genes. As a result, our study not only provides valuable resources for resistance in barley and genetic tools for breeding, but also identifies candidate genes that lay the foundation for cloning HvRHF1. This endeavor will significantly contribute to our understanding of the molecular mechanisms underlying cereal resistance to Hessian fly.

Genetic dissection of Hessian fly resistance in bread wheat (Triticum aestivum L.) using genome-wide association study in Morocco

Hessian fly (HF), Mayetiola destructor (Say), is an important wheat insect pest that annually results in significant production losses. In Morocco, this insect reduces wheat yields by 32–36 % during drought years. The purpose of the current study is to identify the genomic region, marker-trait associations (MTAs), and putative genes associated with the trait of hessian fly resistance in 210 bread wheat (Triticum aestivum L.) genotypes from the International Center for Agricultural Research in Dry Areas (ICARDA). The screening was carried out in the growth chamber using the Hessian fly Mayetiola destructor (Say) populations collected from the Chaouia Ouardigha region in Morocco. The 210 genotypes tested showed various degrees of resistance to the Hessian fly, with eighty-six accessions showing high levels of resistance. The HF severity ranged from 0 to 100 %, whereas the coefficient of variance (CV) was recorded at 84.15 %. Genome-wide association studies (GWAS) using a mixed linear model (MLM) identified 20 significant MTAs at P < 0.001 associated with Hessian fly resistance. The highest number of MTA (10) was recorded in the A sub-genome, followed by 9 MTAs in the B genome. The highest significant marker is AX-95143016 which is located on chromosome 3B with a -Log10(p) of 10.23. After mapping the 20 significant markers associated with Hessian fly resistance, there were 12 potential candidate genes found. This study identified highly resistant genotypes and significant markers that could be used in future wheat breeding programs.

Hessian fly (Diptera: Cecidomyiidae) virulence in Louisiana: assessment of field populations from 2023 to efficacy of 27 Hessian fly resistance genes in wheat.

The Hessian fly, Mayetiola destructor (Say), is one of the most important insect pest plaguing wheat (Triticum aestivum, L) producers across the United States and around the world. Genetic resistance is the stalwart for control of Hessian fly. However, new genotypes (biotypes) arise in deployment of wheat containing resistance genes, so field populations must be evaluated periodically to provide information on the efficacy of those deployed genes. Louisiana (LA), with its diverse agricultural landscape, is not exempt from the challenges posed by this destructive pest. We previously documented the resistance response of wheat lines harboring Hessian fly resistance (H) genes against field populations collected in 2008 from across the southeastern United States, including Iberville Parish, LA. In the spring of 2023, we reevaluated the resistance response of 27 H genes from the field populations collected from Iberville Parish, LA, and compared the results with those observed in 2008. Sixteen H genes showed comparable resistance to the field populations from both years. While 3 of the H genes, H11, H23, and H24, showed a significant decrease in resistance, 2 genes, H16 and H31, had marked increase in resistance. Furthermore, 6 additional H genes were evaluated in 2023, with 4 showing >70% resistance. Our results clearly identify a total of 20 H genes that are moderate to highly effective against the 2023 Hessian fly population from Iberville Parish, LA. The resistance response documented in this study offers valuable information to wheat breeders in the region for effective management of this insect pest.

Comparison of Agro-Phenological and Technological Traits in Advanced Durum Wheat Lines Differing in Reaction to Hessian Fly Infestation

The aim of this study was to compare agro-phenological and technological traits in advanced durum wheat lines differing in responses to Hessian fly larval attacks. A field experiment was carried out during the 2014/2015 cropping season at the main research stations of Marchouch and Tassaoute in a randomized completed block design. Twenty-two durum wheat genotypes comprising twenty advanced lines from the INRA breeding program and two commercial varieties were used in this study. Agro-phenological and grain quality determinations were concerned with plant height, grain yield, days to heading, protein content, wet gluten content, gluten strength, and yellow pigment content. The analysis of variance revealed significant environment, genotype, and genotype-by-environment (G × E) effects for the majority of the measured traits. A high level of heritability was also observed for grain yield (94.9%), followed by gluten strength (90.7%), yellow pigment content (79.3%), wet gluten content (77.79%), plant height (71.5), and protein content (70.02%); moderate levels of heritability were recorded for days to heading (65.8%). The data for Hessian fly resistance in both the field and infested greenhouse demonstrated three distinct group of genotypes: “resistant” with 4 genotypes, “susceptible without field escape to Hessian fly attack” with 16 genotypes, and “susceptible with field escape to Hessian fly attack” with 2 genotypes. The ANOVA analysis indicated the existence of significant differences between groups of genotypes for grain yield, days to heading, protein content, yellow pigment content, and gluten strength at the Tassaoute station, while at the Marchouch site, the differences were significant only for plant height and gluten strength. Protein content and wet gluten content revealed highly significant positive correlations, indicating the possibility of effective selection of the two traits simultaneously. Biplot analysis indicated that the first two Principal Components (PCs) accounted for 56.04% and 56.34% of the relationships between the genotypes and all of the attributes at the Marchouch and Tassaoute sites, respectively. The results of principal component analysis and Cluster based on agro-phenological and grain quality traits categorized the genotypes into three separate groups for the Marchouch site and four groups for the Tassaoute site. Individuals within each group are characterized by well-defined precocity, productivity, and technological criteria. The different behaviors of the lines studied in the present work are of great interest and can be exploited in breeding programs in order to improve agro-phenological and technological traits in durum wheat.

New sources of Hessian fly resistance in Triticum turgidum wheat lines from Asia and Europe

New sources of Hessian fly resistance in Triticum turgidum wheat lines from Asia and Europe

Identification of new sources of Hessian fly resistance in tetraploid wheat

AbstractHessian fly (HF) (Mayetiola destructor Say) is an obligate destructive pest of wheat (Triticum aestivum L.) causing severe economic losses worldwide. Deployment of resistant wheat cultivars harboring HF resistance (H) genes is still the most effective and economical method to manage this insect pest. However, extensive use of H genes can impose selection pressure on HF populations, leading to the development of virulent biotypes that can breakdown plant resistance. Further, increase in environmental temperatures to 25–30°C during the wheat‐growing season can also negatively impact HF resistance, thereby necessitating the identification of new and novel sources of HF resistance and evaluate them for temperature sensitivity. In the current study, we evaluated the phenotypic response of 254 Triticum turgidum (L.) wheat accessions of African origin to Biotype L HF infestation. Of these, 10 accessions exhibited &gt;70% resistance to Biotype L HF infestation. These 10 resistant accessions also showed &gt;70% resistance when screened with vH13 HF biotype. Additionally, these HF resistant lines were evaluated for expression of resistance at a higher temperature of 30°C, and three tetraploid wheat accessions that maintained 100% resistance to Biotype L HF at the increased temperature were identified. These newly identified HF resistant lines offer valuable tools to breeders and farmers that can be used in breeding programs to develop cultivars for durable resistance to HF and efficient crop management.

Registration of LCS ‘Valiant’ hard red winter wheat

AbstractHistorically cultivars developed jointly by the University of Nebraska‐Lincoln and USDA‐ARS wheat (Triticum aestivum L.) improvement project tend to be late and better adapted to the northern Great Plains. LCS ‘Valiant’ (Reg. no. CV‐1196, PI 693223; tested as NE10478‐1) was released based on the merits of its earliness, agronomic performance, relevant disease resistances, and end‐use quality characteristics and its adaptation to the central Great Plains. As such, the line was licensed to Limagrain Cereal Seeds for their ability to market outside of Nebraska. LCS Valiant hard red winter wheat was released in March 2020 by the developing institutions and the licensee. NE10478‐1 was a selection in 2011 for uniformity and grain yield from NE10478, which was derived from the cross NI03418/‘Camelot’. The pedigree of NI03418 is W91‐248/NE95544 (=McVey 78015/NE88521)//‘Thunderbird’. The final cross of NE10478 was made in 2004. The F1 generation was grown in Yuma, AZ, in 2005, and the F2 to F3 generations were advanced as bulks at Mead, NE, in 2006–2007 or sent for Hessian fly resistance screening by the USDA. In 2007, single F3‐derived F4 rows were planted for selection. There was no further selection in NE10478 other than to remove off‐types thereafter until 2011 when heads were selected to increase uniformity. LCS Valiant was evaluated in replicated trials thereafter. It has excellent winter survival, acceptable reactions to many of the common diseases in its target area, and good end‐use quality for bread making.

Reliable DNA Markers for a Previously Unidentified, Yet Broadly Deployed Hessian Fly Resistance Gene on Chromosome 6B in Pacific Northwest Spring Wheat Varieties.

Hessian fly [Mayetiola destructor (Say)] is a major pest of wheat (Triticum aestivum L.) throughout the United States and in several other countries. A highly effective and economically feasible way to control Hessian fly is with resistant cultivars. To date, over 37 Hessian fly resistance genes have been discovered and their approximate locations mapped. Resistance breeding is still limited, though, by the genes’ effectiveness against predominant Hessian fly biotypes in a given production area, genetic markers that are developed for low-throughput marker systems, poorly adapted donor germplasm, and/or the inadequacy of closely linked DNA markers to track effective resistance genes in diverse genetic backgrounds. The purposes of this study were to determine the location of the Hessian fly resistance gene in the cultivar “Kelse” (PI 653842) and to develop and validate Kompetitive Allele Specific PCR (KASP) markers for the resistance locus. A mapping population was genotyped and screened for Hessian fly resistance. The resulting linkage map created from 2,089 Single Nucleotide Polymorphism SNP markers placed the resistance locus on the chromosome 6B short arm, near where H34 has been reported. Three flanking SNPs near the resistance locus were converted to KASP assays which were then validated by fine-mapping and testing a large panel of breeding lines from hard and soft wheat germplasm adapted to the Pacific Northwest. The KASP markers presented here are tightly linked to the resistance locus and can be used for marker-assisted selection by breeders working on Hessian fly resistance and allow confirmation of this Hessian fly resistance gene in diverse germplasm.

Precise mapping of QTL for Hessian fly resistance in the hard winter wheat cultivar 'Overland'.

A major QTL for Hessian fly resistance was precisely mapped to a 2.32 Mb region on chromosome 3B of the US hard winter wheat cultivar 'Overland'. The Hessian fly (HF, Mayetiola destructor) is a destructive insect pest of wheat in the USA and worldwide. Deploying HF-resistant cultivars is the most effective and economical approach to control this insect pest. A population of 186 recombinant inbred lines (RILs) was developed from 'Overland' × 'Overley' and phenotyped for responses to HF attack using the HF biotype 'Great Plains'. A high-density genetic linkage map was constructed using 1,576 single nucleotide polymorphism (SNP)markers generated by genotyping-by-sequencing(GBS). Two quantitative trait loci (QTLs) with a significant epistatic effect on HF resistance were mapped to chromosomes 3B (QHf.hwwg-3B) and 7A (QHf.hwwg-7A) in Overland, which are located in similar chromosome regions as found for H35 and H36 in the cultivar 'SD06165', respectively. QHf.hwwg-3B showed a much larger effect on HF resistance than QHf.hwwg-7A. Five and four GBS-SNPs, respectively, in the QHf.hwwg-3B and QHf.hwwg-7A QTL intervals were converted into Kompetitive allele specific polymerase chain reaction (KASP) markers. QHf.hwwg-3B was precisely mapped to a 2.32Mb interval (2,479,314-4,799,538bp) using near-isogenic lines (NILs) and RILs that have recombination within the QTL interval. The US winter wheat accessions carrying contrasting alleles at KASP markers KASP-3B4525164, KASP-7A47772047 and KASP-7A65090410 showed significant difference in HF resistance. The combination of the two KASP markers KASP-3B3797431 and KASP-3B4525164 is near-diagnostic for the detection ofQHf.hwwg-3B in a US winter wheat panel and can be potentially used for screening the QTL in breeding programs.

Identification of a major QTL for Hessian fly resistance in wheat cultivar ‘Chokwang’

The Hessian fly (HF, Mayetiola destructor) is one of the destructive pests of wheat (Triticum aestivum L.) worldwide. Resistant cultivars can effectively minimize wheat damage due to this insect pest. To identify new quantitative trait loci (QTL) for HF resistance, a population of recombinant inbred lines (RILs) was developed from a cross between the HF-resistant wheat cultivar ‘Chokwang’ and susceptible wheat ‘Ning 7840’, and phenotyped for responses to HF attack. A linkage map was constructed using 1147 single nucleotide polymorphism (SNP) markers generated from genotyping-by-sequencing (GBS). One major QTL, QHf.hwwg-6BS, for HF-resistance was identified on chromosome arm 6BS, which explained up to 84.0% of the phenotypic variation and was contributed by Chokwang. Two RILs showed recombination in the candidate interval of QHf.hwwg-6BS, which delimited QHf.hwwg-6BS to a 4.75 Mb physical interval between 6,028,601 bp and 10,779,424 bp on chromosome arm 6BS of IWGSC Chinese Spring reference genome RefSeq v2.0. Seven GBS-SNPs in the candidate interval were converted into Kompetitive allele specific polymerase chain reaction (KASP) markers. Two of them, KASP-6B112698 and KASP-6B7901215, were validated in a U.S. winter wheat panel. KASP-6B112698 was nearly diagnostic, thus can be used to screen QHf.hwwg-6BS and pyramid it with other resistance genes in breeding programs.

Mapping of a novel major effect Hessian fly field partial-resistance locus in southern soft red winter wheat line LA03136E71.

Hessian fly resistance has centralized around resistance loci that are biotype specific. We show that field resistance is evident and controlled by a single locus on chromosome 7D. Hessian flies (Mayetiola destructor Say) infest and feed upon wheat (Triticum aestivum L) resulting in significant yield loss. Genetically resistant cultivars are the most effective method of Hessian fly management. Wheat breeders in the southern USA have observed cultivars exhibiting a "field resistance" to Hessian fly that is not detectable by greenhouse assay. The resistant breeding line "LA03136E71" and susceptible cultivar "Shirley" were crossed to develop a population of 200 random F4:5 lines using single seed descent. The population was evaluated in a total of five locations in North Carolina during the 2019, 2020, and 2021 seasons. A subsample of each plot was evaluated for the total number of tillers, number of infested tillers, and total number of larvae/pupae. From these data, the percent infested tillers, number of larvae/pupae per tiller, and the number of larvae/pupae per infested tiller were estimated. In all within and across environment combinations for all traits recorded, the genotype effect was significant (p<0.05). Interval mapping identified a single large effect QTL distally on the short arm of chromosome 7D for all environment-trait combinations. This locus was identified on a chromosome where no other Hessian fly resistance/tolerance QTL has been previously identified. This novel Hessian fly partial-resistance QTL is termed QHft.nc-7D. Fine mapping must be conducted in this region to narrow down the causal agents responsible for this trait, and investigation into the mode of action is highly suggested.

‘GA JT141‐14E45’: A new soft red winter wheat cultivar adapted to Georgia and the U.S. Southeast region

AbstractIn Georgia and the southeast region of the United States, acreage of soft red winter wheat (SRWW) (Triticum aestivum L.) has decreased in recent years. There is an urgent need to release new cultivars with high yield potential, resistance to yield‐limiting diseases and insects, and good baking quality to maximize value in regional markets. To address this, the SRWW breeding program at the University of Georgia (UGA), in collaboration with the SUNGRAINS breeding programs, developed ‘GA JT141‐14E45’ (Reg. no. CV‐1183, PI 689519), a SRWW cultivar released by the UGA College of Agricultural and Environmental Sciences and licensed to AGSouth (AGS) Genetics as AGS 3030. GA JT141‐14E45 is widely adapted to the U.S. Southeast, having high yield, good resistance to diseases such as leaf rust, stripe rust, powdery mildew, and Soil‐borne wheat mosaic virus (SBWMV) and to current biotypes of Hessian fly (Mayetiola destructor Say). It has good resistance to Fusarium head blight (FHB) or scab. GA JT141‐14E45 has good grain volume weight and acceptable milling and baking quality. GA JT141‐14E45 was derived from the cross of ‘AGS 2026’/‘Jamestown’. Jamestown was used in the cross mainly for its resistance to FHB (FHB QTL 1A‐Neuse and 1B‐Jamestown). AGS 2026 is a UGA cultivar released in 2007 with very good disease resistance to rusts (Yr17/Lr37/Sr38), Hessian fly resistance (H13), and excellent yield.

Plant Resistance to Cereal and Food Legume Insect pests in North Africa, West and Central Asia: Challenges and Achievements.

Even though host plant resistance has long been recognized as the foundation of integrated pest management, research in North Africa, West and Central Asia only started in 1980. The recent use of Focused Identification of Germplasm Strategy has increased the chance of finding sources of resistance to cereal and food legume pests. The resistant sources have been successfully used in breeding programs to develop resistant germplasm to key cereal and legume pests. The first major locus associated with resistance to Sunn pest at vegetative stage was identified in bread wheat as were two new loci for Hessian fly resistance from Triticum dicoccum and T. araraticum. Combined sources of resistance to several pests have been identified in alien translocation wheat lines.

Registration of the Louise‐Penawawa spring wheat recombinant inbred line mapping population

AbstractThe Louise‐Penawawa spring wheat (Triticum aestivum L.) recombinant inbred line (RIL) mapping population (Reg. no. MP‐13, NSL 535038 MAP) was developed from a cross between the elite soft white spring wheat cultivars ‘Louise’ and ‘Penawawa’ at Washington State University. The population is composed of 180 RILs developed through single seed descent from the F2 to the F5 generation. The population and its parents were genotyped using both simple sequence repeat and single‐nucleotide polymorphism marker platforms. Analysis of markers identified 29 linkage groups that located to all 21 wheat chromosomes. The population was initially developed for the study of high‐temperature adult‐plant stripe rust resistance but has since been phenotyped and used to identify Hessian fly resistance, tan spot resistance, polyphenol oxidase activity, vital agronomic traits, and milling and baking quality. Markers have been identified that are closely linked with quantitative trait loci (QTL) that influence these traits. This population has the potential to identify QTL for additional traits of interest. Additionally, lines from this RIL population are well suited to introgress traits of interest as both Louise and Penawawa are commercially released cultivars adapted to a variety of growing regions and conditions.

The Hessian fly recessive resistance gene h4 mapped to chromosome 1A of the wheat cultivar 'Java' using genotyping-by-sequencing.

The recessive Hessian fly resistance gene h4 and flanking SNP markers were located to a 642kb region in chromosome 1A of the wheat cultivar 'Java.' Hessian fly (HF), Mayetiola destructor, is one of the most destructive insect pests in wheat worldwide. The wheat cultivar 'Java' was reported to carry a recessive gene (h4) for HF resistance; however, its chromosome location has not been determined. To map the HF resistance gene in Java, two populations of recombinant inbred lines (RILs) were developed from 'Bobwhite' × Java and 'Overley' × Java, respectively, and were phenotyped for responses to infestation of HF Great Plains biotype. Analysis of phenotypic data from the F1 and the RIL populations confirmed that one recessive gene conditioned HF resistance in Java. Two linkage maps were constructed using single-nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing (GBS). The h4 gene was mapped to the distal end of the short arm of chromosome 1A, which explained 60.4 to 70.5% of the phenotypic variation for HF resistance in the two populations. The GBS-SNPs in the h4 candidate interval were converted into Kompetitive Allele-Specific Polymerase Chain Reaction (KASP) markers to eliminate the missing data points in GBS-SNPs. Using the revised maps with KASP markers, h4 was further located to a 642kb interval (6,635,984-7,277,935bp). The two flanking KASP markers, KASP3299 and KASP1871, as well as four other closely linked KASP markers, may be useful for pyramiding h4 with other HF resistance genes in breeding.

Identification of two novel Hessian fly resistance genes H35 and H36 in a hard winter wheat line SD06165.

Two new Hessian fly resistance QTLs (H35 and H36) and tightly linked SNP markers were identified in a US hard winter wheat SD06165. Hessian fly (HF), Mayetiola destructor (Say), is one of the most destructive pests in wheat (Triticum aestivum L.) worldwide. Growing resistant cultivars is the most effective approach to minimize Hessian fly damage. To identify new quantitative trait loci (QTLs) for HF resistance, a recombinant inbred line population was developed by crossing HF resistant wheat line SD06165 to a susceptible line OK05312. The population was genotyped with 1709 single-nucleotide polymorphisms (SNPs) generated from genotyping-by-sequencing and phenotyped for HF resistance in greenhouses. Two novel QTLs for HF resistance were identified from SD06165. The major QTL, designated as H35, was closely linked to SNP marker SDOKSNP7679 on chromosome 3BS that explained 23.8% and 36.0% of the phenotypic variations; the minor QTL, designated as H36, was flanked by SNP markers SDOKSNP1618 and SDOKSNP8089 on chromosome 7AS and explained 8.5% and 13.1% of the phenotypic variation in the two experiments. Significant interaction was detected between the two QTLs. Seventeen SNPs that tightly link to H35 and eight SNPs that tightly link to H36 were converted to kompetitive allele specific polymerase chain reaction markers for selecting these QTLs in breeding programs.

Phenotypic and molecular characterization of Hessian fly resistance in diploid wheat, Aegilops tauschii

BackgroundThe Hessian fly (Mayetiola destructor), belonging to the gall midge family (Cecidomyiidae), is a devastating pest of wheat (Triticum aestivum) causing significant yield losses. Despite identification and characterization of numerous Hessian fly-responsive genes and associated biological pathways involved in wheat defense against this dipteran pest, their functional validation has been challenging. This is largely attributed to the large genome, polyploidy, repetitive DNA, and limited genetic resources in hexaploid wheat. The diploid progenitor Aegilops tauschii, D-genome donor of modern-day hexaploid wheat, offers an ideal surrogate eliminating the need to target all three homeologous chromosomes (A, B and D) individually, and thereby making the functional validation of candidate Hessian fly-responsive genes plausible. Furthermore, the well-annotated sequence of Ae. tauschii genome and availability of genetic resources amenable to manipulations makes the functional assays less tedious and time-consuming. However, prior to utilization of this diploid genome for downstream studies, it is imperative to characterize its physical and molecular responses to Hessian fly.ResultsIn this study we screened five Ae. tauschii accessions for their response to the Hessian fly biotypes L and vH13. Two lines were identified that exhibited a homozygous resistance response to feeding by both Hessian fly biotypes. Studies using physical measurements and neutral red staining showed that the resistant Ae. tauschii accessions resembled hexaploid wheat in their phenotypic responses to Hessian fly, that included similarities in larval developmental stages, leaf and plant growth, and cell wall permeability. Furthermore, molecular responses, characterized by gene expression profiling using quantitative real-time PCR, in select resistant Ae. tauschii lines also revealed similarities with resistant hexaploid wheat.ConclusionsPhenotypic and molecular characterization of Ae. tauschii to Hessian fly infestation revealed resistant accessions that shared similarities to hexaploid wheat. Resembling the resistant hexaploid wheat, the Ae. tauschii accessions mount an early defense strategy involving defense proteins including lectins, secondary metabolites and reactive oxygen species (ROS) radicals. Our results reveal the suitability of the diploid progenitor for use as an ideal tool for functional genomics research in deciphering the wheat-Hessian fly molecular interactions.

Susceptibility of North Dakota Hessian Fly (Diptera: Cecidomyiidae) to 31 H Genes Mediating Wheat Resistance.

The agricultural landscape of North Dakota is changing. Corn and soybean are now commonplace, but once were rare. Spring sown wheat Triticum aestivum L. and durum wheat Triticum turgidum spp. durum continue to be dominant, but more winter-sown wheat is expected in the future. The presence of wheat in the landscape throughout much of the year will benefit populations of the Hessian fly, Mayetiola destructor (Say), which occurs throughout the state, sometimes in large numbers. Hessian fly is unusual among crop pests for which resources for plant resistance are well developed. On wheat genotypes expressing a single effective H resistance gene, 100% of larvae die before exhibiting any growth. Over 35 H genes in the public domain are available for crossing into elite cultivars. We explored the effectiveness of 31 Hessian fly resistance genes for a North Dakota Hessian fly population. Six genes-H4, H15, H21, H23, H26, and H29-caused 100% larval mortality. Seven others caused at least 80% mortality. Experimental data were used to address three additional questions. Do adult females avoid laying eggs on plants that will kill their offspring: Are neonate larvae able to detect resistance that will end up killing them? Do all 31 genes confer equal protection against larval-induced growth deficits? North Dakota wheat breeders have the necessary tools to create highly resistant wheat cultivars. So far, H genes have been deployed singly in cultivars. Advances in plant breeding will enable gene stacking, a more durable strategy over time.

Genetic identification of loci for Hessian fly resistance in durum wheat

Durum wheat (Triticum durum Desf.) is a major crop of North Africa. Here, its production is affected by Hessian fly (Mayetiola destructor, HF) epidemics. Genetic resistance against this pest exist, but its molecular basis remains unclear. Here, a panel of 159 modern durum lines were exposed to the Moroccan HF biotype. Association mapping studies revealed three major loci conferring resistance. QH.icd-2A was identified at LOD of 24.1 on the telomeric end of 2AL, and it is believed to represent a novel locus derived from T. dicoccum. QH.icd-5B was identified on 5BS at LOD of 9.5, and it appears as overlapping with H31. QHara.icd-6B was identified at LOD of 54.5. This locus confers resistance to five Moroccan released cultivars, including ‘Faraj’. A mapping population (MP) was obtained by crossing ‘Faraj’ and a HF-susceptible cultivar ‘Gidara2’. Challenging this MP with the Moroccan and Great Plains HF biotypes revealed 1:1 segregation ratio fitting of a single gene. Quantitative trait locus (QTL) analysis confirmed a single locus at LOD of 35 and 25 for the two biotypes, respectively, corresponding to QHara.icd-6B. This locus spans a 7.7 cM interval, and it is derived via introgression from a resistant T. araraticum. One KASP marker (BS00072387) was validated for use in breeding on a separate set of elite lines, to show r2 of 0.65 and accuracy of 0.98. Finally, field testing across sites did not identify any yield drag for QHara.icd-6B. The work presented here provides ideal tools to incorporate HF-resistant loci in durum cultivars via marker-assisted breeding.