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Hessian fly is among the major pests of wheat (Triticum spp.) around the world. We evaluated 18 tetraploid (4X) or durum accessions [Triticum turgidum L. ssp. durum (Desf.) van Slageren], which were sourced from the USDA‐ARS National Small Grains Collection. Two of the most virulent strains of Hessian fly, vH9 and Biotype L, were used to assess the reaction of germplasm to larval attack. A susceptible hexaploid wheat accession (CItr 17790, also known as 'Len') and a resistant tetraploid wheat accession (PI 134942, which is a donor of resistance gene H33), were included as controls during the test. We confirmed previously reported resistant germplasm and identified two novel germplasm accessions that exhibited a clear resistance against vH9 and Biotype L infestation. The data showed that Trigo 87 (Reg. no. GP‐1046, PI 519832, a durum accession from Lebanon) and Iumillo (Reg. no. GP‐1047, PI 519716, a durum accession from India) are both resistant to vH9 infestation. In addition, Trigo 87 is also resistant to Biotype L infestation, while the resistance of Iumillo to Biotype L was inconclusive. These wheat lines can be used directly in durum breeding programs. Moreover, the resistance genes can be transferred to hexaploid wheat backgrounds for use especially in the eastern and southeastern United States, where few options for resistance are available. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is one of the most damaging wheat (Triticum aestivum L.) diseases in humid and semihumid regions around the world. Breeding efforts have focused on resistance mechanisms that limit the spread once a spike is infected--type II resistance. But resistance to initial infection, type I resistance, is an important trait that could be combined with other modes of resistance. The objective of this project was to identify and map the locations of previously unknown quantitative trait loci (QTL) that reduce the incidence of initial infection. A mapping population of 198 recombinant inbred lines (RILs) was evaluated for type I resistance in both the field and greenhouse. A two-enzyme genotyping-by-sequencing (GBS) approach was applied to construct a 1883-cM linkage map yielding single-nucleotide polymorphism (SNP) markers. Composite interval mapping analysis detected a QTL on chromosome 1AS under greenhouse conditions and three other QTL on chromosomes 1BL, 2BL, and 3AS in field environments. Each QTL explained between 7.44 and 12.20% of the total phenotypic variation. Sixteen RILs were identified with markers for all three QTL on chromosomes 1BL, 2BL, and 3AS exhibiting significantly improved type I resistance (a mean of 33.06% improvement) over RILs with none of the three markers in field experiments. Our results also confirmed that types I and II FHB resistance were controlled by different loci in the wheat RIL population and could be used in combination to provide multiple layers of defense for cultivar development through marker-assisted selection. [ABSTRACT FROM AUTHOR]

Hessian fly populations adapt to overcome newly deployed resistance genes within a few years of release. Although more than 34 genes have been identified that confer resistance against Hessian fly [Mayetiola destructor (Say)] attack in wheat (Triticum aestivum L.), only five genes currently provide resistance against fly populations in the southeastern United States. But even these genes are not 100% effective, leaving Georgia and North and South Carolina with between one and three effective genes for cultivar development. With the goal of providing much needed resistance for this region in a wheat line suitable for use with marker-assisted selection, we identified a durum wheat line that confers resistance to Hessian fly populations from Maryland, Delaware, North and South Carolina, and Georgia in 100% of the plants tested. Resistance from this tetraploid durum line, PI 134942, was introgressed into hexaploid common wheat to generate the line 97211. Segregating populations of F2:3 families were constructed with the durum donor and with the common wheat recipient to identify resistance genes and provide flanking markers. Although the resistance of the durum donor appeared to involve more than one gene, one partially dominant but very effective gene, H33, was successfully transferred and identified in the hexaploid recipient. This gene was mapped to the short arm of wheat chromosome 3A and is flanked by single sequence repeat markers xgwm218 and hbg284. [ABSTRACT FROM AUTHOR]

The gene-for-gene interaction triggering resistance of wheat against first-instar Hessian fly larvae utilizes specialized defence response genes not previously identified in other interactions with pests or pathogens. We characterized the expression of Hfr-3, a novel gene encoding a lectin-like protein with 68–70% identity to the wheat germ agglutinins. Within each of the four predicted chitin-binding hevein domains, the HFR-3 translated protein sequence contained five conserved saccharide-binding amino acids. Quantification of Hfr-3 mRNA levels confirmed a rapid response and gradual increase, up to 3000-fold above the uninfested control in the incompatible interaction 3 days after egg hatch. Hfr-3 mRNA abundance was influenced by the number of larvae per plant, suggesting that resistance is localized rather than systemic. In addition, Hfr-3 was responsive to another sucking insect, the bird cherry-oat aphid, but not to fall armyworm attack, wounding or exogenous application of methyl jasmonate, salicylic acid or abscisic acid. Western blot analysis demonstrated that HFR-3 protein increased in parallel to mRNA levels in crown tissues during incompatible interactions. HFR-3 protein was detected in both virulent and avirulent larvae, indicating ingestion. Anti-nutritional proteins, such as lectins, may be responsible for the apparent starvation of avirulent first-instar Hessian fly larvae during the initial few days of incompatible interactions with resistant wheat plants. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) of wheat (Triticum aestivum L.) is a devastating disease in wheat production worldwide. Identifying resistance genes and understanding the genetic basis of resistance to FHB are prerequisites to developing cultivars that can avoid losses from FHB. This investigation of quantitative trait loci (QTL) was performed in a recombinant inbred (RI) population derived from a cross between the FHB-moderately susceptible cv. Patterson and the FHB-resistant line Fundulea 201R (F201R). Bulk DNAs from the 11 most resistant and 12 most susceptible lines of the phenotypic distribution of the RI population, together with the parental lines, were screened with simple sequence repeat (SSR) markers. Regional QTL mapping identified four interval regions, located on chromosomes 1B, 3A, 3D, and 5A, that conferred resistance to FHB. The QTLs located on chromosomes 1B and 3A, contributed by F201R, had large effects and were consistently expressed in three environments. The four QTLs together accounted for 32.7% of the phenotypic variation, or 43.0% of the genotypic variation. The QTL on chromosome 3A is located in the same region as a QTL that was detected in wild tetraploid wheat T. dicoccoides (Koern. ex Asch. & Graebner) Aarons. The possibility that the FHB resistance QTLs of F201R and that of T. dicoccoides on chromosome 3A have the same origin is discussed. [ABSTRACT FROM AUTHOR]