Applied phenomics and genomics for improving barley yellow dwarf resistance in winter wheat

Barley yellow dwarf (BYD) is one of the major viral diseases of cereals. Phenotyping BYD in wheat is extremely challenging due to similarities to other biotic and abiotic stresses. Breeding for resistance is additionally challenging as the wheat primary germplasm pool lacks genetic resistance, with most of the few resistance genes named to date originating from a wild relative species. The objectives of this study were to, i) evaluate the use of high-throughput phenotyping (HTP) to improve BYD assessment, ii) identify genomic regions associated with BYD resistance, and iii) evaluate the ability of genomic selection (GS) models to predict BYD resistance. Up to 107 wheat lines were phenotyped during each of five field seasons under both insecticide treated and untreated plots. Across all seasons, BYD severity was lower within the insecticide treatment along with increased plant height and grain yield compared to untreated entries. Only 9.2% of the lines were positive for the presence of the translocated segment carrying the resistance gene Bdv2. Despite the low frequency, this region was identified through association mapping. Furthermore, we mapped a potentially novel genomic region for BYD resistance on chromosome 5AS. Given the variable heritability of the trait (0.211–0.806), we obtained a predictive ability for BYD severity ranging between 0.06–0.26. Including the presence or absence of Bdv2 as a covariate in the GS models had a large effect for predicting BYD but almost no effect for other observed traits. This study was the first attempt to characterize BYD using field-HTP and apply GS to predict disease severity. These methods have the potential to improve BYD characterization, additionally identifying new sources of resistance will be crucial for delivering BYD resistant germplasm.