LAUSR

Colletotrichum species isolates contain two paralogous CYP51 genes that encode sterol 14-demethylase enzymes, but their role in sensitivity to DMI fungicides is yet to be determined. In this study, each of the two genes from C. fioriniae and C. nymphaeae was able to rescue the function of CYP51 in the yeast Saccharomyces cerevisiae, demonstrating their independent function. Deletion of CYP51A led to increased sensitivity to propiconazole, diniconazole, prothioconazole, cyproconazole, epoxiconazole, flutriafol, prochloraz, and difenoconazole in C. fioriniae, and to the same fungicides and tebuconazole in C. nymphaeae with the exception of prochloraz. Deletion of CYP51B in C. fioriniae and CYP51B in C. nymphaeae made mutants increasingly sensitive to five of nine DMI fungicides tested. The results suggest species-specific, differential binding of DMI fungicides onto the two CYP51 enzymes. Pairing DMIs with different effects on CYP51A and B deletion mutants resulted in synergistic effects as determined in mycelial growth inhibition experiments. Deletion mutants showed no fitness penalty, in terms of mycelial growth, sporulation, and virulence. Our study elucidates the effect of the CYP51A and CYP51B of Colletotrichum spp. on DMI sensitivity, suggesting using mixture of DMIs may improve the efficacy for anthracnose management.