Eucalypt powdery mildew caused by Podosphaera pannosa in Brazil

Abstract

Eucalypt powdery mildew is an important disease in greenhouses and clonal hedges of Eucalyptus spp. in Brazil, which can cause leaf and shoot distortion, shoot discoloration, and growth reduction that results in production losses. Because reliable information regarding the causal agent of the disease is lacking, this study used ITS and 28S rDNA sequencing and morphological analyses to identify the powdery mildew pathogen that occurrs in eucalypt nurseries within different regions in Brazil. Based on the results of morphological characteristics and phylogenetic analyses, the pathogen isolates were identified as Podosphaera pannosa, also known as the rose powdery mildew pathogen. Cross inoculations with pathogen isolates from rose and eucalypt demonstrated that P. pannosa can infect both host species. The ITS sequence-based phylogeny showed that 42 sequences generated in this study were comprised within a single clade containing P. pannosa, which was supported by a posterior probability of 88%. Identical ITS sequences were obtained from all 42 pathogen isolates, which suggests a clonal population.