Multilocus Characterization of Podosphaera fragariae Causing Strawberry Powdery Mildew in Lima, Peru: Evidence from ITS, GAPDH, and RPB2 Phylogeny

Powdery mildew associated with Fragaria × ananassa Duch. has recently been reinterpreted as a species complex comprising Podosphaera fragariae in Eurasia and P. shepherdiae in the Americas; however, molecular data for South American populations remain scarce, and the few South American specimens sequenced to date have been assigned to P. shepherdiae. In this study, the causal agent of powdery mildew on strawberry cultivar 'Sabrina' grown in Lima, Peru, was characterized through morphological analysis, pathogenicity tests, and multilocus phylogenetic inference based on ITS, GAPDH, and RPB2. The fungal material examined developed mycelial colonies typical of powdery mildew and consistently reproduced the symptoms observed in the field. Morphologically, the pathogen exhibited characteristics consistent with Podosphaera sect. Sphaerotheca, including ellipsoidal conidia with conspicuous fibrosin bodies, chained conidiogenesis, and Fibroidium-type lateral germination. Sequences were obtained for ITS, GAPDH, and RPB2. The concatenated ITS+GAPDH+RPB2 phylogeny resolved two major lineages corresponding to P. fragariae (95%) and P. shepherdiae (98%), placing the Peruvian isolate PUCP-Pa001 within the P. fragariae clade with high statistical support and close affinity to Eurasian accessions. These results provide the first multilocus evidence of P. fragariae on cultivated strawberry in the Americas and support the hypothesis of an anthropogenic introduction associated with the international movement of propagative material. Furthermore, the study demonstrates the value of multilocus approaches for resolving cryptic taxa within Erysiphaceae and provides the first South American reference sequences for this pathogen, supporting future epidemiological and phytosanitary research on powdery mildews associated with Fragaria in South America.