Peronospora variabilis Gäum. was observed to be consistently associated with downy mildew of pitseed goosefoot ( Chenopodium berlandieri Moq.). Morphological characteristics of the conidiophores, conidia, and oospores of the oomycete corresponded to those of P. variabilis. The morphological identification was complemented by a phylogenetic analysis of the ITS region. To our knowledge, this is the first report of P. variabilis on C. berlandieri in Mexico.
