Phylogeny of Pseudoperonospora causing downy mildew of Cucurbitaceae in Brazil

Downy mildew of cucurbits is a disease caused by the Oomycete Pseudoperonospora cubensis. It can cause considerable losses in cucurbit crops. Phylogenetic studies point to the existence of cryptic species of Pseudoperonospora. The objective of this study was to determine, the phylogeny of Pseudoperonospora species affecting cucurbits in different regions of Brazil. For this, leaves with symptoms of downy mildew were collected in areas of cucurbits production in the states of Pernambuco, Minas Gerais, Ceara, and the Distrito Federal. For phylogenetic analyses, DNA extraction was performed, and PCR reactions were carried out using primers DC-6 and LR-0, Cox2-F and Cox2-RC4, OomCox1-levup and OomCox1-levlo, FM79-C1 and FMPHY-10b, for amplification of the internal transcribed spacer (ITS) region, the mitochondrial cytochrome c oxidase subunit II (cox2), the mitochondrial cytochrome c oxidase subunit I (cox1) and cox2-cox1 intergenic spacer respectively. The nucleotide sequences were analyzed, edited, and aligned to perform Bayesian Inference analysis. The results of the phylogenetic analyses presented in the cox2-cox1-cox2_1-ITS concatenated tree indicate that in Brazil, the downy mildew of cucurbits is caused by phylogenetically distinct lineages of P. cubensis.

Automated summary

The objective of this study was to determine the phylogeny of Pseudoperonospora species causing downy mildew in cucurbits in different regions of Brazil. Phylogenetic analysis of DNA extracted from diseased leaves revealed that distinct lineages of P. cubensis are responsible for downy mildew of cucurbits in Brazil.