Powdery mildew of California poppy caused by Erysiphe eschscholziae in Mexico

摘要

Severe infection by powdery mildew was observed on California poppy (Eschscholzia californica) plants in Texcoco, State of Mexico, during spring of 2014 to 2017. Symptoms included colonies of white to greyish mildew-like growth on the abaxial and adaxial surfaces of the leaves. The identification of the fungal species was performed by examination of morphological structures using light microscopy and scanning electron microscope (SEM), as well as sequence analysis of the 5'-end of 28S rRNA gene and the internal transcribed spacer (ITS) region of rDNA. Using the combination of morphological characterization and a phylogenetic analysis using Bayesian inference, the fungal agent was identified as Erysiphe eschscholziae. Pathogenicity tests were conducted on leaves of California poppy plants, and Koch's postulates were fulfilled. This is the first report of E. eschscholziae causing powdery mildew on Eschscholzia californica in Mexico.