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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #352223

Research Project: Management of Pathogens for Strawberry and Vegetable Production Systems

Location: Crop Improvement and Protection Research

Title: Comparative genomics of downy mildews

item MICHELMORE, RICHARD - University Of California
item FLETCHER, KYLE - University Of California
item Martin, Frank
item GIL, JULIANA - University Of California
item ZHANG, LIN - University Of California
item WOOD, KELSEY - University Of California
item KENEFICK, AUBREY - University Of California
item DELA CUEVA, FE - University Of The Philippines Los Banos
item Luster, Douglas - Doug
item RIVERA, YASMIN - Animal And Plant Health Inspection Service (APHIS)
item MAGILL, CLINT - Texas A&M University
item SHARMA, RAJAN - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item Klosterman, Steven
item ZHANG, YAN - University Of California
item ABAD, GLORIA - Animal And Plant Health Inspection Service (APHIS)
item REYES-CHIN-WO, SEBASTIAN - University Of California

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/26/2018
Publication Date: 7/28/2018
Citation: Michelmore, R., Fletcher, K., Martin, F.N., Gil, J., Zhang, L., Wood, K., Kenefick, A., Dela Cueva, F., Luster, D.G., Rivera, Y., Magill, C., Sharma, R., Klosterman, S.J., Zhang, Y., Abad, G., Reyes-Chin-Wo, S. 2018. Comparative genomics of downy mildews. International Congress of Plant Pathology, 6th International Oomycetes Workshop: Phytophthora, Pythium, Downy Mildews and Related Genera, July 28, 2018, Boston, Massachusetts.

Interpretive Summary: Downy mildews are obligate pathogens and cannot be cultured, making it a challenge to do genetic analysis with them. With the development of modern DNA sequencing technologies it is possible to sequence and assemble the entire genome of different species, thereby providing a way to make comparisons among different taxa and the identify genes that may be associated with the ability to cause disease and host specificity. This abstract described the efforts that have been made with a range of economically important downy mildews.

Technical Abstract: We have sequenced the genomes of several temperate and tropical downy mildews including Bremia lactucae, Peronospora effusa, P. schachtii and P. tabacina as well as Sclerospora graminicola, Peronosclerospora sorghi, P. maydis, P. philippinensis, and P. sacchari. For some, it was possible to sequence multiple historical and contemporary isolates. These genomes could be assembled to varying degrees of completeness and contiguity. Peronospora spp. have small genomes (~50 Mb), whereas the tropical DMs have larger genomes (>200 Mb). Heterozygosity varies widely; some species are mainly homozygous and were easily assembled, while several are highly heterozygous and remain challenging to assemble. Deep sequencing revealed that some but not all isolates of B. lactucae are heterokaryotic. Extensive synteny is detectable among downy mildews and Phytophthora spp. These assemblies combined with published downy mildew genomes are being used to elucidate taxonomic and evolutionary relationships, to study genome architectures, fluidity, and synteny, and to characterize expression and variation of effector repertoires. Phylogenetic analysis supported multiple origins for biotrophy in downy mildews.