An evolutionary approach identifies and exploits effective FHB resistance in hitherto susceptible wheat germplasm

Abstract

It has proved difficult to combine high FHB resistance with desirable agronomic and quality traits while advancing through cycles of crosses with elite but FHB-susceptible parents. Instead of aiming to transfer the complement of genes that condition FHB resistance in such sources as Sumai 3, our goal is to emulate in the desired germplasm the evolution of resistance that occurred in Sumai 3 as it derived from moderately susceptible parents. Genes in resistance pathways induced by Fusarium inoculation that are present in FHB-resistant wheat lines are also present and expressed in counterpart FHB-susceptible near-isogenic lines. Wheat cultivars and otherwise adapted germplasm may thus already contain the necessary genes but remain susceptible because expression is not coordinated effectively. The required heritable alteration of expression can be induced by growing repeated generations of virus-susceptible wheat plants under pressure from systemic infection with wheat streak mosaic virus (WSMV), as we have shown for such traits as height, maturity and virus resistance. As the components of FHB resistance (PR genes induced by Fusarium) are already present, variations induced by repeated cycles of WSMV infection combined with selection under FHB pressure evolve FHB resistance, apparently de novo, from hitherto susceptible germplasm. We present examples of Canadian bread and durum wheat germplasm that show FHB resistance generated by this approach.