Characterization of Genetic Resistance to Fusarium Head Blight and Bacterial Leaf Streak in Intermediate Wheatgrass (Thinopyrum intermedium)

Intermediate wheatgrass (IWG, Thinopyrum intermedium, (Host) Barkworth & D.R. Dewey subsp. intermedium, 2n = 6x = 42) is a novel perennial crop currently undergoing domestication efforts. It offers remarkable ecosystem services and yields higher relative to other perennial grain crops. While IWG is mostly resistant to Fusarium head blight (FHB), identifying genomic regions associated with resistance will help protect the crop from potential disease epidemics. An IWG biparental population of 108 individuals was developed by crossing parents differing in their response to FHB and bacterial leaf streak (BLS). The population was screened for disease reaction over three years using isolates collected from IWG plants in St. Paul, Minnesota, USA. Linkage maps representing the 21 IWG chromosomes were constructed from 4622 Single Nucleotide Polymorphism (SNP) markers, with one SNP at every 0.74 cM. Interval mapping identified 15 quantitative trait loci (QTL) associated with FHB resistance and 11 with BLS resistance. Models with two or three QTL combinations reduced FHB disease severity by up to 15%, and BLS by up to 17%. When markers associated with FHB resistance were used as cofactors in genomic selection models, trait predictive ability improved by 24-125%. These genomic regions and genetic markers associated with FHB and BLS resistance can also be used to safeguard annual cereal grains through gene introgression and selective breeding.