Investigating effector diversity as a source of cultivar-specific pathogenicity across global isolates of the lettuce bacterial leaf spot pathogen.
Emma Rosenthal: The Pennsylvania State University
<div>Bacterial Leaf Spot of lettuce has a 100-year history in the US, and in the 1990’s it reemerged as a significant threat that breeding programs struggled to counter. Multilocus sequence analysis of global <em>Xanthomonas campestris</em> pv. <em>vitians</em> (<em>Xcv</em>) isolates using four housekeeping genes and evaluation of plant-pathogen interactions has revealed six groups with cultivar-specific resistance. We hypothesize that differences in effector repertoires cause this variation in cultivar-specificity across the genotypic groups. To test this, the genomes of 21 representative isolates of <em>Xcv </em>and relevant types and pathotypes were sequenced, assembled, and annotated. Barcoded libraries were created for each isolate using 2 µg of DNA extract and the Illumina TruSeq DNA PCR-Free kit. An equimolar pool of the libraries for each isolate was sequenced using Illumina MiSeq, generating 250 nt, paired-end reads. Yield was 185 Mb per sample; with the <em>Xcv</em> genome size of 5 MB, that computed to 37x coverage. The sequence data was aligned to a reference genome for assembly and annotation. Bioinformatics tools are being employed to identify sequences belonging to any of the more than 30 known effectors of <em>Xanthomonas</em> plant pathogens. Once these effector repertoires are determined, we will evaluate correspondence between effector repertoire composition and host reaction. This knowledge can be applied in development and deployment of lettuce with resistance across all genotypes of <em>Xcv</em>.</div>
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