Understanding and improving resistance to Hessian fly (Mayetiola destructor) in US wheat using genetic mapping and molecular techniques

Abstract

Hessian fly (Mayetiola destructor) is a worldwide pest of wheat (Triticum spp.) causing significant yield losses. Utilizing resistant varieties of wheat is the most effective method of control, particularly in mild climates. The effectiveness of resistance genes is lost over time due to genetic diversity within fly populations, and most cultivars have only one resistance gene making them vulnerable to this loss of resistance. Thirty‐seven resistance genes have been mapped along with four Hessian fly response genes and 11 novel quantitative trait loci (QTL). The majority of these exhibit antibiotic resistance, but new research suggests two or more novel QTL are associated with a valuable tolerant response. Studies suggest that fitness costs associated with resistance can be overcome after the initial infestation, but this may not hold true with repeated fly attacks and should be considered when pyramiding genes. Several of these genes do show temperature sensitivity, which should also be considered during breeding. Resistance mechanisms include increased levels of salicylic acid, upregulation of oxo‐phytodienoic acid reductase genes and genes responsible for lipid and protein mobilization, and increased synthesis of polyphenols, among others. These mechanisms are part of an effector‐triggered response. Resistant genes and QTL with KASP markers for use in creating gene pyramids include QHf.hwwg‐6BS, Qhara.icd‐6B, h4, H7, H32, H33, H34, H35, and H36. GWAS has been used to screen large numbers of elite breeding lines for resistance to Hessian fly. Marker trait associations discovered through GWAS can potentially be used in creating gene pyramids with multiple pest and pathogen resistance genes.