Link to home

Effector diversity within the US-23 clonal lineage of Phytophthora infestans

Martha Sudermann: Plant Pathology and Plant Microbe Biology Section, Cornell University

<div><em>Phytophthora infestans </em>causes late blight in tomatoes and potatoes. The pathogen was responsible for the Irish Potato Famine in the 1840s, and continues to have significant economic impacts world-wide. The goal of this study is to understand population diversity within the US-23 clonal lineage, which is currently the predominant lineage in the USA. Previous work from our lab based on a genome-wide SNP analysis has shown that diversity exists within this lineage. In a continuation of the work, we are now studying effector diversity within the US-23 clonal lineage using a target enrichment technique called PenSeq, which captures over 500 effectors from the <em>P. infestans</em> genome. The effector sequences of 12 isolates of <em>P. infestans</em> from the US-23 clonal lineage were re-sequenced through PenSeq. Preliminary results showed relatively little effector diversity when comparing presence or absence of known avirulence determinants within each isolate. For example, <em>Avr1 </em>doesn’t appear to be present in any of the 12 US-23 clonal lineage isolates tested. <em>Avr3a </em>and <em>Avr3b </em>appear to be present in all of the isolates tested. AVR3a is represented by two different alleles and the isolates showed some differences in alleles. Two of the isolates contained only the EM form, while the remaining isolates were heterozygous for EM and KI. This proves to be interesting because the encoded protein AVR3a<sup>KI </sup>activates resistance in potatoes but AVR3a<sup>EM</sup> does not. Detached leaf assays will be conducted to validate the preliminary results. RNA-seq will be used to determine expression levels of each effector in each isolate. A complete analysis of the entire effector repertoire of the 12 US-23 isolates is in progress.</div>