Fungicide Resistance to SYP-34773 Mediated by Overexpression of the MFS Gene PoDHA1 in Pyricularia oryzae

Rice blast, caused by Pyricularia oryzae, is a major threat to rice production. SYP-34773, a novel pyrimidinamine fungicide, effectively inhibits P. oryzae, but resistance mechanisms are poorly understood. This study identified eight highly resistant mutants derived from wild-type strain M118, with resistance factors of 120.32-177.78. Notably, their compound fitness index (CFI) values were significantly reduced compared to the parental strain, and they displayed pronounced cross-resistance to diflumetorim and rotenone. Transcriptomic analysis revealed that PoDHA1, encoding a Major Facilitator Superfamily (MFS) transporter, was upregulated 36.12-fold in the resistant mutants treated with SYP-34773. Functional validation through gene overexpression confirmed that PoDHA1 confers resistance to SYP-34773 in P. oryzae strains otherwise sensitive to this fungicide. Furthermore, mutants overexpressing PoDHA1 also exhibited reduced sensitivity to other two mitochondrial complex I inhibitors rotenone and diflumetorim. These findings suggest that MFS transporters, particularly PoDHA1, play a key role in mediating resistance to SYP-34773 in P. oryzae.