Co-Occurrence of Two Phylogenetic Clades of Pseudoperonospora cubensis, the Causal Agent of Downy Mildew Disease, on Oriental Pickling Melon

Abstract

The genus Pseudoperonospora, an obligate biotrophic group of Oomycota, causes the most destructive foliar downy mildew disease on many economically important crops and wild plants. A previously unreported disease by Pseudoperonospora was found on oriental pickling melon (Cucumis melo var. conomon) in Korea, which is a minor crop cultivated in the temperate climate zone of East Asia, including China, Korea, and Japan. Based on molecular phylogenetic and morphological analyses, the causal agent was identified as Pseudoperonospora cubensis, and its pathogenicity has been proven. Importantly, two phylogenetic clades of P. cubensis, harboring probably two distinct species, were detected within the same plots, suggesting simultaneous coexistence of the two clades. This is the first report of P. cubensis causing downy mildew on oriental pickling melon in Korea, and the confirmation of presence of two phylogenetic clades of this pathogen in Korea. Given the high incidence of P. cubensis and high susceptibility of oriental pickling melon to this disease, phytosanitary measures, including rapid diagnosis and effective control management, are urgently required.

Keywords:

• cox2 mtDNA
• downy mildew
• phylogenetic analysis
• Pseudoperonospora humuli

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by grants from the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT & Future Planning [2019R1C1C1002791], Republic of Korea.