Epigenetics Serves Genetics: Fusarium Head Blight (FHB) Resistance in Elite Wheat Germplasm

Current gene introgression-based approaches have made only modest progress toward the goal of developing Canadian wheat cultivars with strong resistance to Fusarium head blight (FHB). Re-examining comparisons of gene induction in resistant and susceptible nearisogenic lines of ‘Sumai 3’, a well-established source of FHB resistance, suggested that resistance was conditioned by effective expression of gene alleles already present in both resistant and susceptible lines. Our alternative approach, based on modifying expression of existing gene alleles, rather than introgressing new ones, aims to preserve the valuable traits accumulated over time by breeders while changing the small number of traits needing improvement. Starting from a single seed of the doubled haploid Canadian wheat cultivar, ‘McKenzie’, successive generations of selfed lines inoculated with Wheat streak mosaic virus (WSMV) evolved resistance to WSMV infection that became genetically fixed with repeated rounds of selection. Some of these lines also evolved improved FHB resistance which has proved stable in three years of testing. Improved resistance to leaf spots, while not specifically selected for, was also recorded in one family of lines, suggesting the versatility of such approaches to crop improvement. In a preliminary agronomic trial conducted in the absence of deliberately applied disease pressure, the evolved line with the best apparent combination of new traits confirmed its promise by equalling or surpassing its ‘McKenzie’ progenitor in the parameters that define the cultivar class. To honour the Scottish philosopher who prepared the ground for evolutionary thinking, we provisionally name this line Hume. _____________________________________________________________________________________________________________