*Correspondence: gang.li@njau.edu.cn (G.L.)

Fusarium head blight (FHB) is a devastating fungal disease of wheat worldwide. Fhb1, a widely used genetic locus of FHB resistance, is successfully applied to wheat breeding across all major wheat-producing regions.

The promising candidate gene of Fhb1, TaHRC, includes susceptible (S) and resistant (R) alleles that are genetically associated with FHB symptoms, the encoding proteins of TaHRC-S and TaHRC-R differ only in their first 21 residues, yet their exact functions in FHB response remain unknown.

Here, we show that two TaHRC alleles opposingly drive liquid-liquid phase separation (LLPS) within a proteinaceous complex, determining FHB susceptibility or resistance. TaHRC-S exhibits stronger LLPS ability than TaHRC-R, which is governed by a cysteine variation at the N-terminus.

We further show that TaHRC recruits a class of proteins with LLPS potentials characterized by their intrinsically disordered regions, referred to as an “HRC hub” within the plant nucleus. TaHRC-S coalesces with hub components via strong LLPS, while TaHRC-R comparatively suppresses the formation of such condensates.

Function of the key hub member TaSR45a, a serine/arginine-rich splicing factor, is dependent upon this TaHRC-driven condensate state, which in turn differentially directs alternative splicing, switching between susceptibility and resistance to wheat FHB.

These findings reveal a mechanism for FHB spread within a spike and shed light on the roles of complex condensates in controlling plant disease.