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United States Department of Agriculture

Agricultural Research Service

Research Project: Detection and Management of Pathogens in Strawberry and Vegetable Production Systems

Location: Crop Improvement and Protection Research

Title: Mitochondrial genomes of Bremia lactucae and development of haplotype markers for population and genetic studies

Authors
item Martin, Frank
item Gil, Juliana -
item Derevnina, Lida -
item Ochoa, Oswaldo -
item Michelmore, Richard -

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 12, 2014
Publication Date: N/A

Interpretive Summary: Bremia lactucae, the causative agent of lettuce downy mildew, is the most important pathogen of lettuce in the US and worldwide. In order to develop cytoplasmic markers for use in population and genetic studies the mitochondrial genome for 28 isolates was assembled and compared to identify regions that are useful for classification of specific mitochondrial types.

Technical Abstract: Bremia lactucae, the causative agent of lettuce downy mildew, is the most important pathogen of lettuce in the US and worldwide. In order to identify cytoplasmic markers for use in population and genetic studies the reference mitochondrial genome of B. lactucae isolate SF5 was assembled from Illumina and Pacific Biosystems reads that had been generated for sequencing the nuclear genome. The SF5 mitochondrial genome is 40,513 bp in size, encodes the 2 rRNAs, 34 genes, 5 putative ORFs and tRNAs common in Pythium and Phytophthora spp.; it also has two unique putative ORFs, a 212 bp inverted repeat encoding duplicate trnK genes, and has 21 copies of an 80 bp repeat. An unusual feature of its organization is the position of the rns coding region; this is in a similar location as in Phytophthora spp. but on the strand opposite to the rnl gene. The mitochondrial genomes have now been assembled for 28 isolates from geographically diverse origins. This revealed polymorphisms due to both SNPs and indels. Network analysis grouped the isolates approximately paralleling their geographic distribution. The relationship between mitochondrial haplotypes and nuclear genotypes and virulence phenotypes will be discussed.

Last Modified: 11/26/2014
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