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Diversity of Venturia inaequalis in Latvia

Olga Sokolova: Institute of Horticulture

<div>The apple scab, caused by an ascomycetous fungus <em>Venturia inaequalis</em> (Cooke) G. Wint., is one of the most important apple diseases worldwide. Due to the <em>V. inaequalis</em> life cycle, in each spring plants are infected by the newly released ascospores representing new genotypes and therefore ensuring the high potential for genetic diversity and adaptation ability of the pathogen. 200 <em>V. inaequalis</em> isolates from 27 apple genotypes from Latvia, and other countries were selected and genotyped using simple sequence repeat (SSR) markers to study genetic diversity of <em>V. inaequalis</em> in Latvia. Thirty-one published primer pairs of SSR were screened, and 14 primer pairs that were amplifying one fragment and showing differences of fragment lengths were used for genotyping. The length of amplified fragments was detected with an automated genetic analyzer and obtained data were combined into one single binary data matrix. The data were analysed by cluster analysis (UPGMA) and Principal Component Analysis (PCA) with computer program "Past" in respect to the host genotype, orchard and geographic region. Two main separate groups were identified among Latvian origin isolates according to the region. Some of the Latvian <em>V. inaequalis</em> isolates showed genetic similarity to isolates virulent on scab-resistant cultivars from other European countries indicating their potential for further virulence development.</div>