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The genomes of Ophiosphaerella spp. reveal new insights into the bermudagrass spring dead spot pathosystem.

Nathalia Graf Grachet: Oklahoma State University

<div>Spring dead spot, caused by <em>Ophiosphaerella herpotricha, O. korrae </em>and <em>O. narmari</em>, is a destructive soilborne disease of turf type bermudagrass in the southern US. <em>Ophiosphaerella</em> appears to switch from a disease-causing necrotroph in susceptible cultivars to an asymptomatic endophyte in resistant cultivars. <em>Ophiosphaerella</em> spp. are described as necrotrophs; however, the mechanisms of pathogenesis are not well understood. The objective of this study was to annotate the protein coding genes <em>Ophiosphaerella</em> spp. to provide clues into pathogenesis. The genomes of 11 isolates and the transcriptomes of 6 isolates were sequenced. Proteins of one isolate of <em>O. herpotricha </em>were validated by mass spectrometry (MS). The functions of protein coding genes were predicted using many functional annotation tools/databases. Genome sizes ranged from 47 Mb to 70 Mb. The number of protein coding genes varied from twelve to fourteen thousand. All isolates had similar abundances of CAZymes (average = 861) with an expansion of plant cell wall degrading enzymes AA families 3, 4, and 11, and CE family 1. Protein search against PHI-base revealed ~40 homologs of avirulence genes. In total, 2,884 <em>O. herpotricha</em> protein-genes were validated by MS, and seven were confirmed homologs of avirulence genes. These results indicate <em>Ophiosphaerella</em> utilizes multiple strategies during pathogenesis.</div>