Orange Wheat Blossom Midge Research Articles

AAC Hassler Canada Western Red Spring wheat

AAC Hassler (PT496) is an early maturing, high yielding, awned and hollow stemmed Canada Western Red Spring (CWRS) wheat (Triticum aestivum L.) cultivar suited to growing conditions in the northern Canadian Prairies. AAC Hassler yielded 8% more than Glenn, 6% more than Parata and 6% more than Carberry in the Parkland Wheat Registration Trials (2019-2021). AAC Hassler matured 4 days earlier than Carberry and had similar maturity as Parata. AAC Hassler had similar height to Glenn and the lodging score was similar to Parata. The test weight of AAC Hassler was 2% lower than the mean of the checks and the thousand kernel weight was similar to Glenn. AAC Hassler had protein content 0.1% higher than Carberry. AAC Hassler expressed an intermediate resistant reaction to Fusarium head blight (FHB; Fusarium graminearum Schwabe). AAC Hassler was moderately resistant to the prevalent races of stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn) and moderately susceptible to common bunt [Tilletia caries (DC) Tul. & C. Tul.]. It was resistant to prevalent races of leaf rust (Puccinia triticina Erikss.) and stripe rust (Puccinia striiformis Westend). AAC Hassler was susceptible to orange wheat blossom midge (OBWM) (Sitodiplosis mosellana Géhin). AAC Hassler was registered under the CWRS class.

Volatile Organic Compounds Mediate Host Selection of Wheat Midge, Sitodiplosis Mosellana (Géhin) (Diptera: Cecidomyiidae) between Preanthesis and Postanthesis Stages of Wheat.

The orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), is a significant wheat pest in the Prairie Provinces of Canada and northern regions of the USA. Wheat phenology plays a critical role in wheat midge oviposition. We hypothesized that S. mosellana oviposition behaviour is influenced by volatile organic compounds (VOCs) emitted by wheat at two adjacent wheat growth stages: preanthesis and postanthesis. A higher number of S. mosellana eggs laid on preanthesis than postanthesis spikes in an oviposition choice experiment using the susceptible spring wheat cultivar 'Roblin'. In preanthesis, wheat emitted higher amounts of Z-3-hexenyl acetate (Z3-06:OAc) than at the postanthesis stage. Higher amounts of methyl ketones such as 2-tridecanone, 2-pentadecanone, and 2-undecanone were emitted by wheat in the postanthesis stage and these VOCs were sensitive to S. mosellana antennae used in the Gas Chromatography-Electroantennographic Detection. Females were attracted to synthetic Z3-06:OAc but were deterred by 2-tridecanone relative to the solvent control in the vertical Y-tube olfactometer. 2-Undecanone and 2-pentadecanone did not show any attractiveness or deterrence. In a no-choice oviposition experiment, fewer eggs were laid in preanthesis wheat exposed to a synthetic VOC blend of Z3-06:OAc, 2-undecanone, 2-tridecanone, and 2-pentadecanone at the concentrations released by postanthesis spikes. This study shows that the reduction of Z3-06:OAc, in the VOC mix, and possibly the increase in 2-tridecanone, are likely responsible for the reduction in oviposition on postanthesis wheat. These results elucidate for the first time the role of specific VOCs mediating S. mosellana oviposition in preanthesis and postanthesis wheat.

Wheat Long Noncoding RNAs from Organelle and Nuclear Genomes Carry Conserved microRNA Precursors Which May Together Comprise Intricate Networks in Insect Responses.

Long noncoding RNAs (lncRNAs) are a diverse class of noncoding RNAs that are typically longer than 200 nucleotides but lack coding potentials. Advances in deep sequencing technologies enabled a better exploration of this type of noncoding transcripts. The poor sequence conservation, however, complicates the identification and annotation of lncRNAs at a large scale. Wheat is among the leading food staples worldwide whose production is threatened by both biotic and abiotic stressors. Here, we identified putative lncRNAs from durum wheat varieties that differ in stem solidness, a major source of defense against wheat stem sawfly, a devastating insect pest. We also analyzed and annotated lncRNAs from two bread wheat varieties, resistant and susceptible to another destructive pest, orange wheat blossom midge, with and without infestation. Several putative lncRNAs contained potential precursor sequences and/or target regions for microRNAs, another type of regulatory noncoding RNAs, which may indicate functional networks. Interestingly, in contrast to lncRNAs themselves, microRNAs with potential precursors within the lncRNA sequences appeared to be highly conserved at the sequence and family levels. We also observed a few putative lncRNAs that have perfect to near-perfect matches to organellar genomes, supporting the recent observations that organellar genomes may contribute to the noncoding transcript pool of the cell.

Modular synthesis of the pheromone (2S,7S)-2,7-nonanediyl dibutyrate and its racemate and their field efficacy to control orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae).

Sudden outbreaks of the orange wheat blossom midge, Sitodiplosis mosellana (Géhin) cause huge wheat yield losses. Use of sex pheromones is more efficient than laborious egg counting to monitor these hidden-concealed insects. Quick synthesis of the sex pheromones is therefore required to meet the sudden outbreak needs. A synthetic approach of stereospecific and racemic S. mosellana pheromones was presented. This method afforded the stereospecific and racemic S. mosellana pheromones in three steps and high enantioselectivity (> 98% ee for (2S,7S)-2,7-nonanediyl dibutyrate) in less than 1 day with 74% and 73% overall yields, respectively, whereas most conventional methods require longer synthesis time with less than 40% yield. The synthesis routes could quickly and economically afford the pheromones, starting from synthon (S)-but-3-yn-2-ol (1a) or but-3-yn-2-ol (1b), through the same three-step processes of coupling, reduction, and esterification. The Y-tube olfactometer results showed significant attractiveness of the synthetic stereospecific and racemic sex pheromones to S. mosellana males relative to the blank control (P < 0.001). Field trials also demonstrated significant attractiveness of the synthetic stereospecific and racemic sex pheromones relative to the blank control (P < 0.001). This modular approach is conducive to the deployment of field traps and timely responses to S. mosellana outbreaks and can be a time-saving and cost-effective tool to manage S. mosellana. © 2022 Society of Chemical Industry.

A chromosome-level genome assembly of the orange wheat blossom midge, Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae) provides insights into the evolution of a detoxification system.

The orange wheat blossom midge Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae), an economically important pest, has caused serious yield losses in most wheat-growing areas worldwide in the past half-century. A high-quality chromosome-level genome for S. mosellana was assembled using PacBio long read, Illumina short read, and Hi-C sequencing technologies. The final genome assembly was 180.69 Mb, with contig and scaffold N50 sizes of 998.71 kb and 44.56 Mb, respectively. Hi-C scaffolding reliably anchored 4 pseudochromosomes, accounting for 99.67% of the assembled genome. In total, 12,269 protein-coding genes were predicted, of which 91% were functionally annotated. Phylogenetic analysis indicated that S. mosellana and its close relative, the swede midge Contarinia nasturtii, diverged about 32.7 MYA. The S. mosellana genome showed high chromosomal synteny with the genome of Drosophila melanogaster and Anopheles gambiae. The key gene families involved in the detoxification of plant secondary chemistry were analyzed. The high-quality S. mosellana genome data will provide an invaluable resource for research in a broad range of areas, including the biology, ecology, genetics, and evolution of midges, as well as insect–plant interactions and coevolution.

Genetic Insight Into the Insect Resistance in Bread Wheat Exploiting the Untapped Natural Diversity.

Climate change is an undeniable threat to sustainable wheat production in the future as an increased temperature will significantly increase grain loss due to the increased number of generations per season of multivoltine species that are detrimental to plants. Among insects, orange wheat blossom midge (OWBM), yellow wheat blossom midge (YWBM), saddle gall midge (SGM), thrips, and frit fly (FF) are important wheat pests in the European environments, which can be managed by the development of resistant cultivars. This involves the identification, confirmation, and incorporation of insect resistance sources into new high-yielding cultivars. We used two diverse and unrelated wheat [winter wheat (WW) and spring wheat (SW)] panels to associate single-nucleotide polymorphism (SNP) markers with the mentioned pests using the tools of association mapping. All in all, a total of 645 and 123 significant associations were detected in WW and SW, respectively, which were confined to 246 quantitative trait loci. Many candidate genes were identified using the BLAST analysis of the sequences of associated SNPs. Some of them are involved in controlling the physical structures of plants such as stomatal immunity and closure, cuticular wax in leaf blade, whereas others are involved in the production of certain enzymes in response to biotic and abiotic stresses. To our knowledge, this is the first detailed investigation that deals with YWBM, SGM, thrips, and FF resistance genetics using the natural variation in wheat. The reported germplasm is also readily available to breeders across the world that can make rational decisions to breed for the pest resilience of their interest by including the resistant genotypes being reported.

Transcriptomic and Metabolomic Analysis of Wheat Kernels in Response to the Feeding of Orange Wheat Blossom Midges (Sitodiplosis mosellana) in the Field.

The orange wheat blossom midge (Sitodiplosis mosellana Géhin) is an insect pest that feeds on wheat (Triticum aestivum L.). The resistance mechanisms of wheat to S. mosellana infestation are largely unknown. In this study, the wheat varieties LX99 and 6218 were identified as highly resistant and susceptible, respectively, via field investigations conducted over two consecutive years. Morphological and microstructural observations of mature wheat kernels following S. mosellana infestation revealed that the degree of cell structure damage in resistant LX99 grains was less than that in susceptible 6218 grains. Transcriptomic and metabolomic analyses of seeds following S. mosellana feeding showed that the differentially expressed genes and differentially accumulated metabolites from LX99 were mostly enriched in several primary and secondary metabolic pathways, including phenylpropanoid biosynthesis, flavonoid biosynthesis, and phenylalanine biosynthesis. Additionally, phenylpropanoid- and flavonoid-related gene expression was significantly upregulated following S. mosellana infestation in LX99 relative to that in 6218. Some metabolites involved in phenylpropanoid/flavonoid pathways, such as cinnamic acid, coumarin, epigallocatechin, and naringenin, were only induced in infested LX99 kernels. These results suggest that phenylpropanoid/flavonoid pathways play important roles in wheat kernel resistance to S. mosellana attack and provide useful insights for the breeding and utilization of resistant varieties.

AAC Whitehead hard white spring wheat

AAC Whitehead, an awned hard white spring wheat (Triticum aestivum L.) cultivar, combines high grain yield and good agronomic characteristics with excellent disease resistance. Based on 34 station-years of registration trial data from 2017 to 2019, AAC Whitehead had grain yield significantly higher than all of the check cultivars. AAC Whitehead had maturity similar to the checks, low lodging scores, and significantly shorter plant height than Snowstar and Whitehawk. AAC Whitehead had significantly lower test weight and higher kernel mass than than all the check cultivars. AAC Whitehead expressed resistance to the prevalent races of leaf, stripe and stem rust, and common bunt; and moderate resistance to Fusarium head blight (FHB). It also expressed tolerance to the orange wheat blossom midge. AAC Whitehead expresses quality attributes within the range of the check cultivars and is eligible for grades of Canada Western Hard White Spring wheat.

AAC Awesome special purpose spring wheat

AAC Awesome is a high yielding spring wheat (Triticum aestivum L.) cultivar eligible for the Canada Western Special Purpose (CWSP) wheat class. Based on 29 site-years of testing over 3 years in the General Purpose Wheat Registration trial (2013–2015), AAC Awesome yielded 14% more grain than AC Andrew, and surpassed yields of Sadash, 5702PR, and Pasteur by 12%, 22%, and 9%, respectively. AAC Awesome had similar maturity, was slightly taller, had higher test weight and larger kernels as compared to AC Andrew. AAC Awesome had excellent levels of resistance to the prevalent races of leaf, stem and stripe rust. It expressed an intermediate level of resistance to Fusarium head blight (FHB), common bunt and loose smut. It also expressed tolerance to the orange wheat blossom midge. AAC Awesome is eligible for grades of Canada Western Special Purpose Wheat class.

AAC Castle red spring wheat

AAC Castle, an awned hard red spring wheat (Triticum aestivum L.), cultivar, combines high grain yield and good agronomic characteristics with excellent resistance to leaf, stem, stripe rust, common bunt and loose smut. It also expressed tolerance to the orange wheat blossom midge. Based on 39 station years of data in the registration trials from 2014 to 2016, the grain yield of AAC Castle was about 17% higher than 5700PR but similar to the other checks. AAC Castle was significantly shorter than AAC Foray and CDC Terrain, but had similar lodging resistance and maturity. AAC Castle had higher test weight, protein concentration, falling number and flour yield than AAC Foray and CDC Terrain. AAC Castle is eligible for grade of the Canada Prairie Spring Red wheat market class.

The orange wheat blossom midge promotes fusarium head blight disease, posing a risk to wheat production in northern China

Fusarium head blight (FHB) and the orange wheat blossom midge (OWBM) are chronic wheat diseases and pest insects, respectively, that share the wheat ear as a host from anthesis to milk development in northern China. To elucidate the interactions between the OWBM and FHB on the ears of wheat, we designed a series of experiments investigating FHB disease severity and OWBM performance in wheat exposed to FHB and OWBM individually or in combination. Our results indicated that wheat ears infected with a combination of OWBM and FHB had greatly increased disease incidence, disease severity, FHB index, FDK (Fusarium damaged kernels) and ISK index (incidence, severity, and, kernel quality index) relative to plants treated only with FHB. Furthermore, the mean percentage of OWBM infected plants and mean number of OWBM larvae per plant were slightly higher than those of plants treated with only OWBM. Wheat ears infected with a combination of OWBM and FHB showed significantly reduced yield relative to those infected by OWBM or FHB alone. These results improve our understanding of the risk posed by OWBM involvement in FHB disease epidemiology and indicate that more-comprehensive risk management may be crucial to advancing integrated pest management of wheat.

Characterization of trehalose metabolic genes and corresponding enzymatic activities during diapause of Sitodiplosis mosellana

Trehalose plays crucial roles in energy metabolism and stress tolerance in various organisms. The orange wheat blossom midge Sitodiplosis mosellana, a serious pest of wheat worldwide, undergoes long obligatory diapause as a larva to survive harsh temperature extremes in summer and winter. To gain an insight into trehalose function and metabolic mechanism in this process, we measured the content of trehalose and glucose, as well as enzymatic activities of trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP) and soluble trehalase (Treh1) at pre-diapause, diapause and post-diapause larvae of S. mosellana. Trehalose levels greatly increased upon entry into diapause, peaked in low-temperature quiescence phase, and significantly dropped after resumption of development, highly consistent with activity changes of trehalose-synthetic enzymes SmTPS and SmTPP. In marked contrast, the activity of trehalose-degrading SmTreh1 exhibited a completely reversed profile. This profile was in agreement with contents of its product i.e. glucose. Furthermore, deduced amino acid sequences of cloned SmTPS, SmTPPB, SmTPPC, SmTreh1-1 and SmTreh1-2 genes contained all conserved functional domains, motifs and active sites. Expression patterns of these genes were closely correlated with their enzyme activities. These results suggested that coordination of trehalose synthetic and degradation pathways is responsible for diapause-related trehalose accumulation, which may serve as an energy reserve for post-diapause development and a cryoprotectant against cold stress in winter.

AAC Hodge Canada western red spring wheat

AAC Hodge (BW1069) is a hollow-stemmed, awned and high yielding Canada Western Red Spring (CWRS) wheat cultivar suited to the growing conditions in Western Canada. AAC Hodge was 6% higher yielding than AAC Viewfield, the highest yielding check in the Central Bread Wheat Cooperative (CBWC) registration trials (2017–2019). Within the same test, AAC Hodge was 16% higher yielding than Carberry. AAC Hodge matured 1 d earlier than Carberry and 2 d later than Unity; Unity is the earliest maturing check in the eastern prairie growing conditions. AAC Hodge was 7 cm shorter with better lodging resistance than Unity. The lodging score for AAC Hodge was lower than the mean of the checks. The test weight of AAC Hodge was similar to the mean of the checks. Over the 3 yr of testing (2017–2019), the 1000-kernel weight of AAC Hodge was equal to, or higher than all the checks. The grain protein content of AAC Hodge was equal to that of AAC Viewfield. AAC Hodge was rated moderately resistant to Fusarium head blight (FHB; Fusarium graminearum Schwabe) and resistant to leaf rust (Puccinia triticina Erikss.), stripe rust (Puccinia striiformis Westend), stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. &amp; E. Henn), and common bunt [Tilletia caries (DC) Tul. &amp; C. Tul.]. AAC Hodge ranged from resistant to moderately susceptible for its reaction to the Ug99 family of stem rusts. AAC Hodge was resistant to orange wheat blossom midge (OBWM) (Sitodiplosis mosellana Géhin). AAC Hodge was registered under the CWRS class.

AAC Succeed durum wheat

AAC Succeed durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.] is adapted to the durum production area of the Canadian prairies. AAC Succeed carries the Sm1 gene, which confers antibiosis-based resistance to orange wheat blossom midge [Sitodiplosis mosellana (Gehin)]. Averaged over three years, AAC Succeed yielded significantly more grain than Strongfield (7%) and AC Navigator (21%). AAC Succeed had a protein concentration significantly higher than Brigade and AC Navigator, and similar to Strongfield. AAC Succeed had significantly stronger straw as measured by lodging score than Strongfield, and similar to Brigade. AAC Succeed is eligible for grades of Canada Western Amber Durum, has low grain cadmium concentration, and has higher yellow pigment concentration than the check cultivars.

Genetic analysis of oviposition deterrence to orange wheat blossom midge in spring wheat.

A major QTL for oviposition deterrence to orange wheat blossom midge was detected on chromosome 1A in the Canadian breeding line BW278 that was inherited from the Chinese variety Sumai-3. Orange wheat blossom midge (OWBM, Sitodiplosis mosellana Géhin, Diptera: Cecidomyiidae) is an important insect pest of wheat (Triticum aestivum L.) that reduces both grain yield and quality. Oviposition deterrence results in a reduction of eggs deposited on spikes relative to that observed on a wheat line preferred by OWBM. Quantification of oviposition deterrence is labor-intensive, so wheat breeders require efficient DNA markers for the selection of this trait. The objective of this study was to identify quantitative trait loci (QTL) for oviposition deterrence in a doubled haploid (DH) population developed from the spring wheat cross Superb/BW278. The DH population and check varieties were evaluated for OWBM kernel damage from five field nurseries over three growing seasons. QTL analysis identified major effect loci on chromosomes 1A (QSm.mrc-1A) and 5A (QSm.mrc-5A). Reduced kernel damage was contributed by BW278 at QSm.mrc-1A and Superb at QSm.mrc-5A. QSm.mrc-1A mapped to the approximate location of the oviposition deterrence QTL previously found in the American variety Reeder. However, haplotype analysis revealed that BW278 inherited this oviposition deterrence allele from the Chinese spring wheat variety Sumai-3. QSm.mrc-5A mapped to the location of awn inhibitor gene B1, suggesting that awns hinder OWBM oviposition. Single-nucleotide polymorphisms (SNPs) were identified for predicting the presence or absence of QSm.mrc-1A based upon haplotype. Functional annotation of candidate genes in 1A QTL intervals revealed eleven potential candidate genes, including a gene involved in terpenoid biosynthesis. SNPs for QSm.mrc-1A and fully awned spikes provide a basis for the selection of oviposition deterrence to OWBM.

Transcriptome analysis of Sitodiplosis mosellana Gehin by RNA-Seq

The wheat midge,Sitodiplosis mosellana,is one of the most important pests in the world.The study aims to get transcriptome of S.mosellana.The transcriptome of S.mosellana was sequenced using an Illumina HiSeq TM 2000 platform.There were 27.88 G datas was obtained which further assembled into 59257 Unigenes with the length of 49861164 bp.Minimum length was 201 bp,maximum length was 29282 bp,average length was 841 bp.Based on the NR,NT,Swiss-Prot,KEGG,GO and KOG databases(Evalue e≤10-10),95029 Unigenes were annotated.In this study,all assembled Unigenes can be broadly divided into biological processes,cellular components and molecular function categories of 50 branches by gene ontology,including metabolic process,binding,catalytic activity and cellular process.Unigenes were further annotated based on KOG category,11279 Unigenes were annotated,which could be grouped into 24 functional categories.In KEGG pathways identification,9110 sequences were annotated,respectively belong to 5 kinds of cellular processes,environmental information process,genetic information process,metabolic and organism system,which can be broadly divided into 32 classes according to the function,including cell growth and apoptosis,cell motility,signal transduction,energy metabolism etc.CDS prediction showed that 30088 sequences can be encoded,which accounted for all the 50.78%.There were 36323 SSR in 59257 Unigenes were,the incidence was 61.30%.The orange wheat blossom midge transcriptome greatly improves our genetic understanding and provides a platform for functional genomics research of this species.

AAC LeRoy Canada Western Red Spring wheat

AAC LeRoy (BW1049) is a hollow stemmed, awned, high-yielding Canada Western Red Spring (CWRS) wheat suited to the growing conditions in western Canada. AAC LeRoy was 10% higher yielding than Unity, the highest yielding check in the Central Bread Wheat Cooperative registration trials (2015–2017). Within the same test, AAC LeRoy was 13% higher yielding than Carberry, a popular CWRS wheat variety across the Canadian Prairies. AAC LeRoy matured 2 d earlier than Carberry and 1 d later than Unity, the earliest maturing check suited for eastern prairie growing conditions. AAC LeRoy was 6 cm shorter with better stem strength than Unity. The lodging score for AAC LeRoy was lower than the mean of the checks. The test weight of AAC LeRoy was similar to the mean of the checks. Over the 3 yr of testing (2015–2017), the 1000-kernel weight of AAC LeRoy was higher than all of the checks, with a grain protein content 0.6% units lower than Carberry. AAC LeRoy was rated as moderately resistant to Fusarium head blight (Fusarium graminearum Schwabe), leaf rust (Puccinia triticina Erikss.), stripe rust (Puccinia striiformis Westend.), and stem rust (Puccinia graminis Pers. f. sp. tritici Erikss. &amp; E. Henn), including the Ug99 family of stem rusts. It also had a resistant reaction to loose smut [Ustilago tritici (Pers.) Rostr.] and an intermediately resistant reaction to common bunt [Tilletia caries (DC.) Tul. &amp; C. Tul.]. AAC LeRoy was resistant to orange wheat blossom midge (Sitodiplosis mosellana Géhin). AAC LeRoy was registered under the CWRS market class.

AAC Magnet Canada Western Red Spring wheat

AAC Magnet (BW1045) is an awned, hollow-stemmed, high-yielding Canada Western Red Spring (CWRS) wheat adapted to growing conditions in the Canadian Prairies. AAC Magnet was 5% higher yielding than Glenn and yielded 2% more than Carberry, a popular CWRS wheat variety across the Canadian Prairies. AAC Magnet matured 2 d earlier than Carberry and a day later than Unity, the earliest maturing check. AAC Magnet had the same height as Glenn and was shorter with better stem strength compared with Unity. AAC Magnet had better lodging scores compared with Unity. Over the 3 yr of testing (2015–2017), the test weight of AAC Magnet was slightly lower than the lowest checks, whereas the 1000-kernel weight of AAC Magnet was higher than all of the checks. The grain protein content of AAC Magnet was 0.3% lower than Carberry. AAC Magnet was rated moderately resistant to Fusarium head blight (Fusarium graminearum Schwabe), resistant to leaf rust (Puccinia triticina Erikss.) and stem rust (Puccinia graminis Pers. f. sp. tritici Erikss. &amp; E. Henn). AAC Magnet was moderately susceptible/susceptible to resistant to the Ug99 family of stem rusts, resistant to loose smut [Ustilago tritici (Pers.) Rostr.], intermediately resistant to stripe rust (Puccinia striiformis Westend.), susceptible to common bunt [Tilletia caries (DC.) Tul. &amp; C. Tul.], and moderately susceptible to leaf spot complex. AAC Magnet was susceptible to orange wheat blossom midge (Sitodiplosis mosellana Géhin). Based on the milling and baking performance over 3 yr (2015–2017) evaluated by the Grain Research Laboratory, Canadian Grain Commission, AAC Magnet was classified as CWRS wheat.

Molecular mapping of major QTL conferring resistance to orange wheat blossom midge (Sitodiplosis mosellana) in Chinese wheat varieties with selective populations.

Two novel midge resistance QTL were mapped to a 4.9-Mb interval on chromosome arm 4AL based on the genetic maps constructed with SNP markers. Orange wheat blossom midge (OWBM) is a devastating insect pest affecting wheat production. In order to detect OWBM resistance genes and quantitative trait loci (QTL) for wheat breeding, two recombinant inbred line (RIL) populations were established and used for molecular mapping. A total of seven QTL were detected on chromosomes 2D, 4A, 4D and 7D, respectively, of which positive alleles were all from the resistant parents except for the QTL on 7D. Two stable QTL (QSm.hbau-4A.2-1 and QSm.hbau-4A.2-2) were detected in both populations with the LOD scores ranging from 5.58 to 29.22 under all three environments, and they explained a combined phenotypic variation of 24.4-44.8%. These two novel QTL were mapped to a 4.9-Mb physical interval. The single-nucleotide polymorphism (SNP) markers AX-109543456, AX-108942696 and AX-110928325 were closely linked to the QTL and could be used for marker-assisted selection (MAS) for OWBM resistance in wheat breeding programs.

Screening for differential expression of genes for resistance to Sitodiplosis mosellana in bread wheat via BSR-seq analysis.

Five putative candidate genes for OWBM resistance in Chinese winter wheat 'Jimai 24' were identified via BSR-seq and differential expression analyses. Orange wheat blossom midge (OWBM), Sitodiplosis mosellana, is one of the most serious threats to wheat production worldwide. Conventional gene mapping methods to identify genes require significant amounts of financial support and time. Here, bulked segregant RNA-seq (BSR-seq) was applied to profile candidate genes and develop associated markers for OWBM resistance. Previously, we identified a major QTL (QSm.hebau-4A) for OWBM resistance on the long arm of chromosome 4A. In this study, we aimed at screening differentially expressed resistance genes associated with this QTL. Twelve differentially expressed genes (DEGs) were obtained based on BSR-seq and differential expression analyses. Among them, four were confirmed to be associated with OWBM resistance via quantitative reverse transcription PCR, using an additional set of wheat samples subjected to OWBM invasion. One SPI-like gene and one Malectin-like gene were revealed by gene annotation, respectively. Sequencing results confirmed that the four DEGs and the SPI gene had SNP polymorphisms between wheat parents. All these five resistance-related genes for OWBM were located in the same genomic region with QSm.hebau-4A. Furthermore, six new markers developed based on sequences of the five genes were also mapped in the same genomic region using genetic population. These five genes may be the candidate genes for OWBM resistance in Chinese wheat 'Jimai 24' and should be the targets for further positional isolation.