Genetic variability and DMI fungicide sensitivity of the Alternaria alternata species group associated with wheat in Uruguay

Abstract

This study provides the first assessment of occurrence, genetic variability, and DMI fungicide sensitivity of wheat-associated Alternaria spp. in Uruguay. Seventy asymptomatic wheat grain samples collected during the 2022 harvest were analyzed. Alternaria spp. were detected in all samples, with infection rates of 19–91% (mean 62%). Of 150 isolates, 55 were assigned to the A. alternata species group. Partial histone H3 sequencing of 19 representative isolates revealed seven haplotypes and two amplicon-size groups. Sensitivity to four DMIs varied among fungicides, with a significant group × fungicide interaction. The 546-bp group showed 2.6-fold higher tebuconazole EC₅。 values. These findings provide baseline sensitivity data and reveal genetic and phenotypic variability within the species group.