Evolution of an <i>Eleusine</i>-Specific Subgroup of <i>Pyricularia oryzae</i> Through a Gain of an Avirulence Gene

Abstract

<i>Eleusine</i> isolates (members of the <i>Eleusine</i> pathotype) of <i>Pyricularia oryzae</i> are divided into two subgroups, EC-I and EC-II, differentiated by molecular markers. A multilocus phylogenetic analysis revealed that these subgroups are very close to <i>Eragrostis</i> isolates. EC-II and <i>Eragrostis</i> isolates were exclusively virulent on finger millet and weeping lovegrass, respectively, while EC-I isolates were virulent on both. The avirulence of EC-II on weeping lovegrass was conditioned by an avirulence gene, <i>PWL1</i>. All EC-II isolates shared a peculiar structure (P structure) that was considered to be produced by an insertion (or translocation) of a DNA fragment carrying <i>PWL1</i>. On the other hand, all EC-I and <i>Eragrostis</i> isolates were noncarriers of <i>PWL1</i> and shared a gene structure that should have predated the insertion of the <i>PWL1</i>-containing fragment. These results, together with phylogenetic analyses using whole-genome sequences, suggest that the <i>Eleusine</i>-specific subgroup (EC-II) evolved through a loss of pathogenicity on weeping lovegrass caused by a gain of <i>PWL1</i>.