Hessian Fly Research Articles

Variable effects of mycorrhizal fungi on predator-prey dynamics under field conditions.

Interactions between herbivores and their predators are shaped, in part, by plant phenotype. Consequently, ubiquitous symbionts of plants below-ground, such as arbuscular mycorrhizal fungi (AMF), may influence interactions above-ground between predators and their prey by altering plant phenotype. However, the ecological relevance of below-ground organisms on predator-prey interactions under field conditions remains unclear. We assessed how AMF influence herbivore-predator interactions through a field experiment. We planted two milkweed species (Asclepias curassavica and Asclepias incarnata) provided with different amounts of AMF inoculum (zero, medium, and high) in a randomized block design. We added aphids to plants and reduced predator pressure weekly for 5weeks to evaluate effects of AMF on predator recruitment. We then allowed herbivore-predator interactions to re-establish naturally for the remainder of the season to examine whether AMF-mediated variation in predator recruitment influenced the suppression of aphid populations. Arbuscular mycorrhizal fungi availability in soils mediated interactions between predaceous aphid midge flies Aphidoletes aphidimyza and their aphid prey Aphis nerii, but the effects were plant species-specific. On A. curassavica, by mid-season, midges were recruited most strongly on plants under medium AMF availability and least on plants under high AMF availability. In contrast, each midge killed fewer aphids with increasing aphid density on medium AMF plants, but killed more aphids with increasing aphid density on high AMF plants. In combination, aphid mortality rates imposed by midges were greatest on medium AMF plants, followed by high and zero AMF plants. By comparison, on A. incarnata, the recruitment of midges was strongest on high AMF plants and weakest on medium AMF plants. AMF had no effect on the number of aphids killed per midge, relative to aphid density, so mortality rates of aphids imposed by midges mirrored recruitment. Rates of decline in aphid populations following predator recolonization were associated with midge densities, as well as lacewing and syrphid densities, which were unaffected by AMF availability. Therefore, the effects of AMF on aphid population decline were not a simple function of AMF-midge interactions. Our findings demonstrate that the availability of AMF in soils has pervasive, but complex, effects on predator-herbivore dynamics in the field.

De Novo Whole-Genome Assembly of the Swede Midge (Contarinia nasturtii), a Specialist of Brassicaceae, Using Linked-Read Sequencing.

The swede midge, Contarinia nasturtii, is a cecidomyiid fly that feeds specifically on plants within the Brassicaceae. Plants in this family employ a glucosinolate-myrosinase defense system, which can be highly toxic to nonspecialist feeders. Feeding by C. nasturtii larvae induces gall formation, which can cause substantial yield losses thus making it a significant agricultural pest. A lack of genomic resources, in particular a reference genome, has limited deciphering the mechanisms underlying glucosinolate tolerance in C. nasturtii, which is of particular importance for managing this species. Here, we present an annotated, scaffolded reference genome of C. nasturtii using linked-read sequencing from a single individual and explore systems involved in glucosinolate detoxification. The C. nasturtii genome is similar in size and annotation completeness to that of the Hessian fly, Mayetiola destructor, but has greater contiguity. Several genes encoding enzymes involved in glucosinolate detoxification in other insect pests, including myrosinases, sulfatases, and glutathione S-transferases, were found, suggesting that C. nasturtii has developed similar strategies for feeding on Brassicaceae. The C. nasturtii genome will, therefore, be integral to continued research on plant-insect interactions in this system and contribute to effective pest management strategies.

Mayetiola destructor (Diptera: Cecidomyiidae) host preference and survival on small grains with respect to leaf reflectance and phytohormone concentrations

The Hessian fly Mayetiola destructor (Diptera: Cecidomyiidae) is a major pest of wheat, globally. We conducted a series of laboratory choice and no-choice assays to quantify Hessian fly host preference for barley (cv. Champion), oat (cv. Cayuse), susceptible (cv. Alturas), and resistant (cv. Hollis) wheat. In addition, larval survivorship and adult emergence were compared among the evaluated host plants. We then examined whether insect preference for a host can be explained by differences in plant spectral reflectance. Further, larval survivorship and adult emergence were compared among host plants in relation to phytohormone concentrations. Hessian flies laid more eggs on wheat compared to either oat or barley. Spectral reflectance measurements of leaves were similar between susceptible and resistant wheat cultivars but different from those of barley and oat. Our results suggested that higher reflectance in the near-infrared range and lower reflectance in the visible range may be used by females for host selection. Hessian fly larvae were unable to develop into the pupal stage on resistant wheat and oat. No significant difference in larval survivorship was detected between the susceptible wheat and barley. However, adult emergence was significantly higher on barley than the susceptible wheat. Phytohormonal evaluations revealed that salicylic acid (SA) may be an important contributor to plant defense response to larval feeding as relatively higher concentrations of SA were present in oat and resistant wheat. While resistance in the resistant wheat is achieved only through antibiosis, both antibiosis and antixenosis were in effect rendering oat as a non-host for Hessian flies.

Insect derived extra oral GH32 plays a role in susceptibility of wheat to Hessian fly

The Hessian fly is an obligate parasite of wheat causing significant economic damage, and triggers either a resistant or susceptible reaction. However, the molecular mechanisms of susceptibility leading to the establishment of the larvae are unknown. Larval survival on the plant requires the establishment of a steady source of readily available nutrition. Unlike other insect pests, the Hessian fly larvae have minute mandibles and cannot derive their nutrition by chewing tissue or sucking phloem sap. Here, we show that the virulent larvae produce the glycoside hydrolase MdesGH32 extra-orally, that localizes within the leaf tissue being fed upon. MdesGH32 has strong inulinase and invertase activity aiding in the breakdown of the plant cell wall inulin polymer into monomers and converting sucrose, the primary transport sugar in plants, to glucose and fructose, resulting in the formation of a nutrient-rich tissue. Our finding elucidates the molecular mechanism of nutrient sink formation and establishment of susceptibility.

Seasonal emergence patterns ofSitodiplosis mosellana(Diptera: Cecidomyiidae) in the Peace River region, Alberta, Canada

AbstractWheat midge,Sitodiplosis mosellanaGéhin (Diptera: Cecidomyiidae), is an invasive pest of wheat,Triticumspp. (Poaceae), in North America and is found in all wheat-growing regions of the world. Wheat midge biology, particularly post-diapause emergence of adults, varies with geographic region. The biology of wheat midge has not previously been examined in the northernmost area of its range in Canada – the Peace River region of Alberta. Wheat midge adult emergence was comparedin situto two phenological models of wheat midge emergence developed in other geographic regions. In-field adult emergence did not match the published phenological models. In the Peace River region, adults emerged later than are predicted by both models and precision for both models was low. With the Saskatchewan model, accumulated rainfall that was more than 110 mm in May and early June delayed emergence, whereas accumulated rainfall that was less than 43 mm during that period caused earlier than predicted emergence. Multiple peaks of wheat midge emergence, up to 20 days apart, were observed at some sites, supporting the Jacquemin model depicting “waves” of emergence. Including differences in soil temperature accumulation related to precipitation and optimising the model temperature thresholds would improve accuracy of the current Canadian phenological model in the Peace River region.

Effect of temperature on the expression of resistance to Hessian fly (Diptera: Cecidomyiidae) in durum wheat cultivars

Hessian fly, Mayetiola destructor (Say) is a destructive insect pest occurring in many wheat growing areas of the world. The most effective management option for controlling Hessian fly is the use of resistant wheat cultivars carrying specific resistance genes. However, wheat resistance genes to Hessian fly are affected by temperature. Two Moroccan cultivars ‘Chaoui’ and ‘Marouane’ and three ICARDA elites DWHF01, DWHF02 and Icamoram7 all carrying resistance to Moroccan Hessian fly populations were evaluated at three different temperatures (20, 25 and 30 °C). Results showed that the elite DWHF01 and DWHF02 resistance was less affected by higher temperatures with percentage of resistant plants remaining above 60% at 30 °C. However, ‘Marouane’, ‘Icamoram7’ and ‘Chaoui’ lost more than 50% of their resistance at 30 °C. Resistance in all these genotypes was expressed only as antibiosis with presence of dead first instars on resistant plants. The number of live larvae on susceptible plants was counted and larval density decreased with increasing temperature. Moreover, length measurements of live larvae showed significant differences across different temperatures, the size of larvae increased as temperature increased and ranged between 3.23 and 4.13 mm. In light of the warming climates and increase occurrence of days above 30 °C during the first months of the Moroccan wheat season, the data presented here are meant to help breeders recommend cultivars better adapted to the raising temperatures.

Wheat Yield in a Tolerant Winter Wheat Line Infested by Hessian Fly (<i>Mayetiola destructor</i>)

The Hessian fly, Mayetiola destructor, is a harmful pest of wheat (Triticum aestivum). Pioneer variety 25R78 is putatively tolerant, meaning that the plant can survive successful Hessian fly infestation with reduced growth effects. To understand if Hessian fly-tolerance in wheat results in reduced yield effects and to analyze the economic feasibility of tolerant wheat as a Hessian fly control method, this study focused on analyzing the effect of infestation on tolerant wheat yield. This study analyzed tolerant Pioneer variety 25R78, resistant Pioneer brand variety 25R32, and susceptible Pioneer brand variety 25R47 through harvest. Treated plants were infested using a plastic cover and allowing 1 - 2 female flies to lay eggs for two hours. We measured head, fertile head number and tiller number. Seeds were analyzed by measuring total seed number and weight, as well as average seed number and weight. Tolerant and resistant plants showed no significant effects on yield in comparison to susceptible wheat. The infested tolerant plants were comparable in yield to infested resistant plants. Therefore, we propose that tolerance incorporated into wheat varieties will lower selection pressure on Hessian fly populations and increase the durability of these wheat lines.

Nonhost Kitaake rice displays phenotypic characteristics of host resistant wheat and molecular biomarkers of both resistant and susceptible wheat in response to feeding by Hessian fly larvae

ABSTRACT The Hessian fly causes severe economic losses in host wheat. The genome complexity of hexaploid wheat makes functional characterization of candidate defense genes extremely challenging. Kitaake rice, a model and simpler genome, exhibits responses resembling nonhost resistance to Hessian fly. Larvae feeding on Kitaake rice plants do not develop beyond first-instars similar to resistant host wheat, although, they show prolonged survival. Kitaake nonhost differs from nonhost Brachypodium, where some larvae develop into second-instars. Kitaake rice plants exhibit a molecular response similar to not only resistant but also susceptible host wheat for six Hessian fly-responsive biomarker genes assayed. Further, in Kitaake, lectins and secondary metabolites may play an important role in early defense preventing the larvae from developing. The phenotypic and molecular characterization of Kitaake rice reveals its suitability as a surrogate model genome for undertaking downstream functional genomics studies of candidate wheat genes that respond to Hessian fly larval attack.

Registration of ‘KS Silverado’ hard white winter wheat

Abstract‘KS Silverado’ (Reg. no. CV‐1175, PI 693936) hard white winter wheat (Triticum aestivum L.) was developed at the Agricultural Research Center–Hays, Kansas State University, and released by the Kansas Agricultural Experiment Station in 2019. KS Silverado was selected from a three‐way cross KS05HW122‐5‐2//KS05HW15‐2‐2/KS06HW46‐3 made in 2008 at Hays, KS. The objective of this cross was to develop a hard white winter wheat cultivar that is adapted to Kansas. KS Silverado was selected as an F6–derived line using a modified bulk method and tested in yield trials across Kansas for five years. KS Silverado is medium‐early and medium‐short and has good straw strength, above average grain volume weight, and very competitive grain yield in western and central Kansas. KS Silverado is tolerant to preharvest sprouting and has a good resistance package to diseases and insects, including Wheat streak mosaic virus, leaf rust, Soilborne wheat mosaic virus, and Hessian fly. It also has good milling and bread‐making qualities.

NGS-based multiplex assay of trait-linked molecular markers revealed the genetic diversity of Iranian bread wheat landraces and cultivars

NGS-based multiplex assay has accomplished a valuable status as a means of high throughput research, rapid screening functional markers in wheat breeding programs. Accordingly, we applied a total of 42 locus-specific markers from Indel and SNP-mediated categorisations coupled with the agronomic important genes or quantitative trait loci (QTL) in bread wheat. The amplicons were analysed by an Ion Torrent Proton Sequencer. Then, an allele detection custom pipeline was applied to process the genotype of a total of 99 Iranian cultivars and 270 landraces. On the whole, 29 markers were positively incorporated and achieved 100% SNP call rates. Assessment of sequence-tagged site (STS) and competitive allele-specific PCR (KASP) markers concerning the same loci confirmed the genotype calls of all markers altogether. It was revealed that the Iranian cultivars and landraces supply a rich genetic resource capable of resisting Hessian fly, leaf rust, fusarium head blight, adult plant leaf diseases, stem rust, wheat soilborne mosaic virus, wheat streak mosaic, pre-harvest sprouting, high grain protein, and gluten strength traits. This finding can be developed to improve and enrich bread wheat. Further, it is advocated that NGS-based multiplex assay can be a promising approach for high throughput in examining trait-linked markers in wheat germplasm collections.

Soft red winter wheat ‘GA 051207‐14E53’: Adapted cultivar to Georgia and the U.S. Southeast region

AbstractSoft red winter wheat (SRWW) (Triticum aestivum L.) is a major crop in Georgia and the U.S. Southeast (SE) region. Hence, new cultivars with high yield potential, high resistance levels to predominant pests, and adequate quality parameters are required to capture and maximize regional market values. Therefore, the University of Georgia SRWW breeding program in collaboration with the SUNGRAINS breeding programs, aims to develop and release SRWW cultivars adapted to Georgia and the SE wheat region with high yield, quality, and pest resistance. ‘GA 051207‐14E53’ SRWW (Reg. no. CV‐1168, PI 689518) was developed and released by the University of Georgia and licensed to AGSouth Genetics Company in 2017 under the name AGS 3040. GA 051207‐14E53 is well adapted to Georgia and the SE region. It has high yield and high resistance to leaf rust, stripe rust, and Soil‐borne wheat mosaic virus. It has medium resistance to powdery mildew and to biotypes C and O of Hessian fly and is resistant to biotypes B and L. GA 051207‐14E53 has good Fusarium head blight resistance. GA 051207‐14E53 possesses H9, Sbm1, and the 2NS:2AS alien introgression from Aegilops ventricosa Tausch, having the Yr17/Lr37/Sr38 genes that protect it against these pests. Grain volume weight and milling and baking qualities of GA 051207‐14E53 are good and meet the SRWW grade standards.

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.

Distribution, population dynamics and damage of Hessian fly, Mayetiola destructor (Diptera: Cecidomyiidae) in North Tunisia

AbstractA three years survey and monitoring studies (2013–2014–2015) were carried out through 4 regions of north Tunisia in order to follow the evolution of the distribution, the frequency of occurrence and damage caused by the Hessian fly Mayetiola destructor (Say) to bread wheat (Triticum aestivum L.) and durum wheat (Triticum durum Desf). Moreover, the effectiveness of resistance genes H3, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, H22, H23, H25 and H26 to protect wheat from Hessian fly attack was assessed in natural field and under controlled laboratory conditions at INRAT‐Kef Station. Results showed that Hessian fly was detected in 60.33% and 51.5% of all sampled durum and bread wheat fields, respectively. This pest was more frequent with a higher percentage of infestation in semi‐arid regions. Indeed, during 2013, infestation rate attained 12.39% in Kef region against 0.9% registered in Bizerte region. In order to update information about the annual number of generations, we surveyed the population dynamic of Hessian fly in Kef region. Three generations of the fly were counted annually on wheat, with two complete and one incomplete generation. This insect affects host plant growth at different developmental stages. Plant height was the most affected parameter followed by shoot dry weight and tiller number. Field investigations on host resistance revealed that among the 16 tested resistance genes, and only three were strictly effective (H22, H25 and H26). The resistance genes H5, H9, H13 and H9H13 have also conferred high levels of protection against Hessian fly. This work indicated that H22, H25 and H26 genes could be incorporated into Tunisian wheat varieties and released to farmers to manage the threat due to Hessian fly attacks.

Analysis of the count of populations and harmfulness of phytophages of agrocenoses of grain cereals of the Central ForestSteppe of Ukraine

The count of harmful entomofauna, damage to plants by phytophages and the proportion of their colonization of soft wheat (winter and spring) and common barley (spring) in the Central Forest-Steppe of Ukraine in the spring-summer period of 2004–2019 were analyzed. Such specialized pests as: leafhoppers (Macrosteles laevis Ribaut, Psammotettix alienus L., Calligypona striatella Fall.), aphids (Schizaphis graminum (Rondani), Macrosiphum (Sitobion) avenae (F.), Brachycolus (Cuernavaca) noxius Mordv., Rhopalosiphum padi (L.)), grain bugs (Eurygaster integriceps Put., Eurygaster maura L., Eurygaster austriaca Schrank, Aelia acuminata L.), wheat trips (Haplothrips tritici Kurd.), common ground beetle (Zabrus tenebrioides Goeze), аnisoplia austriaca beetle (Anisoplia austriaca Herbst, Anisoplia segetum Herbst), grain flea beetles (Phyllotreta vittula Redt., Chaetocnema hortensis Geoffr., Chaetocnema aridula Gyll.), cereal leaf beetle (Oulema melanopus (L.), Oulema lichenis Voet.), cereal flies (Oscinella frit L., Oscinella pusila Meigen, Mayetiola destructor (Say), Phorbia securis Tiensuu etc.) were the most common in agrocenoses of grain crops in a harmful entomocomplex. Polyphagous insects, namely caterpillars of gnawing scoops (Scotia segetum Schiff., Scotia exclamationis L.), also caused significant damage in cereal crops. It was revealed that a complex of sucking pests is numerous on winter wheat, represented by wheat thrips (Haplothrips tritici Kurd.), Cereal aphids (Macrosiphum (Sitobion) avenae F., Schizaphis graminum Rond.), Grain sawflies (Cephus pygmaeus L., Trachelus tabidus F.), on spring wheat grain flea beetles (Phyllotreta vittula Redt., Chaetocnema aridula Gyll.) and wheat thrips, on spring barley – grain flea beetles and cereal aphids. Under favorable conditions for overwintering, warm, moderately humid weather in spring and dry weather in summer, active colonization and an increase in the number of phytophages led to their exceeding in 2.5–5.7 times of the economic threshold of harmfulness. Under these conditions, the number of grain bugs (Eurygaster integriceps Put., Е. austriacus Schrnk., Е. maura L., Aelia acuminata L., Dolycoris baccarum L.) in some years reached 8– 15 ind./m2 , ground beetles — up to 20 ind./m2, grain beetles — up to 17 ind./m2, cereal aphids — up to 50 ind./plant.

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.

Microbial Inoculants Differentially Influence Plant Growth and Biomass Allocation in Wheat Attacked by Gall-Inducing Hessian Fly (Diptera: Cecidomyiidae).

Beneficial root microbes may mitigate negative effects of crop pests by enhancing plant tolerance or resistance. We used a greenhouse experiment to investigate impacts of commercially available microbial root inoculants on growth and biomass allocation of wheat (Triticum aestivum L. [Cyperales: Poaceae]) and on survival and growth of the gall-inducing wheat pest Hessian fly, Mayetiola destructor (Say). A factorial design was used, with two near-isogenic wheat lines (one susceptible to Hessian fly, the other resistant), two levels of insect infestation (present, absent), and four inoculants containing: 1) Azospirillum brasilense Tarrand et al. (Rhodospirillales: Azospirillaceae), a plant growth-promoting bacterium, 2) Rhizophagus intraradices (N.C. Schenck & G.S. Sm.) (Glomerales: Glomeraceae), an arbuscular mycorrhizal fungus, 3) A. brasilense + R. intraradices, and 4) control, no inoculant. Larval feeding stunted susceptible wheat shoots and roots. Plants had heavier roots and allocated a greater proportion of biomass to roots when plants received the inoculant with R. intraradices, regardless of wheat genotype or insect infestation. Plants receiving the inoculant containing A. brasilense (alone or with R. intraradices) had comparable numbers of tillers between infested and noninsect-infested plants and, if plants were susceptible, a greater proportion of aboveground biomass was allocated to tillers. However, inoculants did not impact density or performance of Hessian fly immatures or metrics associated with adult fitness. Larvae survived and grew normally on susceptible plants and mortality was 100% on resistant plants irrespective of inoculants. This initial study suggests that by influencing plant biomass allocation, microbial inoculants may offset negative impacts of Hessian flies, with inoculant identity impacting whether tolerance is related to root or tiller growth.

Differential localization of Hessian fly candidate effectors in resistant and susceptible wheat plants.

Hessian fly Mayetiola destructor is a notorious pest of wheat. Previous studies suggest that Hessian fly uses effector‐based mechanisms to attack wheat plants during parasitism, but no direct evidence has been reported to support this postulation. Here, we produced recombinant proteins for five Family‐1 candidate effectors and antibodies. Indirect immunostaining and western blots were carried out to examine the localization of Hessian fly Family‐1 proteins in plant and insect tissues. Confocal images revealed that Family‐1 putative effectors were exclusively produced in the basal region of larval salivary glands, which are directly linked to the mandibles’ ducts for effector injection. The five Family‐1 proteins were detected in infested host plants on western blots. Indirect immunostaining of sectioned host tissues around the feeding site revealed strikingly different localization patterns between resistant and susceptible plants. In susceptible plants, the Family‐1 proteins penetrated from the feeding cell into deep tissues, indicative of movement between cells during nutritive cell formation. In contrast, the Hessian fly proteins were primarily limited to the initially attacked cells in resistant plants. The limitation of effectors’ spread in resistant plants was likely due to wall strengthening and rapid hypersensitive cell death. Cell death was found in Nicotiana benthamiana in association with hypersensitive reaction triggered by the Family‐1 effector SSGP‐1A2. Our finding represents a significant progress in visualizing insect effectors in host tissues and mechanisms of plant resistance and susceptibility to gall midge pests.

Diverse Wheat-Alien Introgression Lines as a Basis for Durable Resistance and Quality Characteristics in Bread Wheat.

Wheat productivity has been significantly improved worldwide through the incorporation of novel genes from various gene pools, not least from wild relatives of wheat, into the commonly cultivated bread and durum wheat. Here, we present and summarize results obtained from a diverse set of wheat-alien introgression lines with mainly introgressions of rye, but also of Leymus spp. and Thinopyrum junceiforme into bread-wheat (Triticum aestivum L.). From this material, lines carrying 2RL were found with good agronomic performance and multiple resistance not least towards several races of powdery mildew. A novel resistance gene, one of few showing resistance towards all today identified stem rust races, designated Sr59, was also found originating from 2RL. Lines with multiple introgressions from 4R, 5R, and 6R were found resistant towards the majority of the stripe rust races known today. Due to lack of agricultural adaptation in these lines, transfer of useful genes into more adapted wheat material is a necessity, work which is also in progress through crosses with the CSph1b mutant, to be able to only transfer small chromosome segments that carry the target gene. Furthermore, resistance towards Russian wheat aphid was found in lines having a substitution of 1R (1D) and translocations of 3DL.3RS and 5AL.5RS. The rye chromosomes 1R, 2R, and 6R were found responsible for resistance towards the Syrian Hessian fly. High levels of especially zinc was found in several lines obtained from crosses with Leymus racemosus and Leymus mollis, while also some lines with 1R, 2R, or 5R showed increased levels of minerals and in particular of iron and zinc. Moreover, lines with 1R, 2R, 3R, and Leymus spp. introgressions were also found to have a combination of high iron and zinc and low cadmium concentrations. High variation was found both in grain protein concentration and gluten strength, measured as %UPP, within the lines, indicating large variation in bread-making quality. Thus, our study emphasizes the impact that wheat-alien introgression lines can contribute to current wheat lines and shows large opportunities both to improve production, resistance, and quality. To obtain such improvements, novel plant breeding tools, as discussed in this paper, opens unique opportunities, to transfer suitable genes into the modern and adapted wheat cultivars.

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.

BSA-Seq Discovery and Functional Analysis of Candidate Hessian Fly (Mayetiola destructor) Avirulence Genes.

The Hessian fly (HF, Mayetiola destructor) is a plant-galling parasite of wheat (Triticum spp.). Seven percent of its genome is composed of highly diversified signal-peptide-encoding genes that are transcribed in HF larval salivary glands. These observations suggest that they encode effector proteins that are injected into wheat cells to suppress basal wheat immunity and redirect wheat development towards gall formation. Genetic mapping has determined that mutations in four of these genes are associated with HF larval survival (virulence) on plants carrying four different resistance (R) genes. Here, this line of investigation was pursued further using bulked-segregant analysis combined with whole genome resequencing (BSA-seq). Virulence to wheat R genes H6, Hdic, and H5 was examined. Mutations associated with H6 virulence had been mapped previously. Therefore, we used H6 to test the capacity of BSA-seq to map virulence using a field-derived HF population. This was the first time a non-structured HF population had been used to map HF virulence. Hdic virulence had not been mapped previously. Using a structured laboratory population, BSA-seq associated Hdic virulence with mutations in two candidate effector-encoding genes. Using a laboratory population, H5 virulence was previously positioned in a region spanning the centromere of HF autosome 2. BSA-seq resolved H5 virulence to a 1.3 Mb fragment on the same chromosome but failed to identify candidate mutations. Map-based candidate effectors were then delivered to Nicotiana plant cells via the type III secretion system of Burkholderia glumae bacteria. These experiments demonstrated that the genes associated with virulence to wheat R genes H6 and H13 are capable of suppressing plant immunity. Results are consistent with the hypothesis that effector proteins underlie the ability of HFs to survive on wheat.