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

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.

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.

Untapped Sources of Dual Resistance to Hessian Fly and Greenbug in Synthetic Hexaploid Wheats

The Hessian fly (Hf) and greenbugs (Gb) are major pests of wheat, causing severe economic losses globally. Deploying resistant wheat is the most effective strategy for managing these destructive insects. However, the resistance is not effective against all Hf or Gb biotypes and can impose selection pressure on insects, resulting in the development of virulent biotypes. These challenges must be met through the discovery of new and novel sources of resistance to these pests. Synthetic Hexaploid Wheat (SHW)-developed cultivars are a rich source of resistance against a diverse array of pathogens and pests. In this study, 80 SHW lines were evaluated for their resistance to Hf and Gb under controlled environmental conditions. Of these, a total of 36 SHW lines showed resistance independently to Hf biotype L and Gb biotype E, while 27 lines showed combined resistance to both Hf and Gb. Further, a subset of 10 SHW lines showed resistance to additional Hf biotypes, Great Plains and vH13. The identification of SHW lines resistant to multiple insects and biotypes offers an invaluable resource to breeders who are looking to stack resistance traits to develop elite cultivars as a strategy to alleviate economic impacts upon global wheat production.

Characterization of the swede midge, Contarinia nasturtii, first instar larval salivary gland transcriptome

Proteins in saliva of gall-forming insect larvae govern insect-host plant interactions. Contarinia nasturtii, the swede midge, is a pest of brassicaceous vegetables (cabbage, cauliflower, broccoli) and canola. We examined the salivary gland (SG) transcriptome of first instar larvae reared on Brassica napus and catalogued genes encoding secreted proteins that may contribute to the initial stages of larval establishment, the synthesis of plant growth hormones, extra-oral digestion and evasion of host defenses. A significant portion of the secreted proteins with unknown functions were unique to C. nasturtii and were often members of larger gene families organized in genomic clusters with conservation patterns suggesting that they are undergoing selection.