Genome-Enabled Insights into Downy Mildew Biology and Evolution

Abstract

Oomycetes that cause downy mildew diseases are highly specialized, obligately biotrophic phytopathogens that can have major impacts on agriculture and natural ecosystems. Deciphering the genome sequence of these organisms provides foundational tools to study and deploy control strategies against downy mildew pathogens (DMPs). The recent telomere-to-telomere genome assembly of the DMP Peronospora effusa revealed high levels of synteny with distantly related DMPs, higher than expected repeat content, and previously undescribed architectures. This provides a road map for generating similar high-quality genome assemblies for other oomycetes. This review discusses biological insights made using this and other assemblies, including ancestral chromosome architecture, modes of sexual and asexual variation, the occurrence of heterokaryosis, candidate gene identification, functional validation, and population dynamics. We also discuss future avenues of research likely to be fruitful in studies of DMPs and highlight resources necessary for advancing our understanding and ability to forecast and control disease outbreaks.