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Novel characteristics of Phytophthora infestans causing late blight on potato in Ethiopia

Jonathan Yuen: Swedish University of Agricultural Sciences

<div><em>Phytophthora infestans</em> causes late blight of potato and tomato. In this study, two distinct groups of <em>P. infestans</em> isolates are reported based on morphological and molecular characters. The isolates were recovered from 300 single lesion leaf samples collected from potato in western and southern Ethiopia. The pathogen DNA was isolated using a cetyltrimethyl-ammonium-bromide protocol. Live cultures were isolated from an actively growing lesion of 100 leaves. Mitochondrial DNA (mtDNA) analysis clearly separated the isolates into two distinct groups. One of the groups corresponds to a known <em>P. infestans</em> haplotype but the other is different with a distinct mtDNA and atypical morphological characters. Restriction fragment length polymorphism analysis established that the isolates in the latter group produced novel band patterns at two mtDNA regions. DNA sequencing of the mtDNA confirmed that the isolates represented a previously unknown variant of <em>Phytophthora</em> attacking <em>Solanum</em> <em>tuberosum</em>. The isolates produced papillate sporangia and chlamydospores that distinguished them from typical <em>P. infestans </em><em>isolates</em>. All isolates were mating type A1 and the novel groups constituted a single clonal population that was genetically identical with a dominant lineage of <em>P. infestans</em> across nine microsatellite markers. This study provided new insight into a previously unknown variability within <em>P. infestans</em> in a region of the world where the pathogen population has rarely been studied.</div>