In planta expression profiles and sequence variation of the endopolygalacturonase gene in Venturia nashicola, the causal agent of Asian pear scab

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Venturia nashicola, causing scab disease on Japanese and Chinese pears, is one of the most devastating pathogens of these crops. Previous studies suggested the potential role of endopolygalacturonase (endoPG) during the invasion stage and sequence variations of the endoPG gene were thought to be effective for pathological race identification. To reveal the role of endoPG during the infection stage, the expression profiles of the endoPG gene of V. nashicola were examined in susceptible and resistant pear cultivars. In the susceptible cv. Kousui, although the biomass of V. nashicola race 1 isolate increased after inoculation, the relative level of endoPG expression decreased obviously. By contrast, in the race-specific resistant pear strain Mamenashi 12, the expression of endoPG increased significantly until 3 dpi though the biomass fluctuated transiently after inoculation. These results indicated that endoPG may not be a crucial factor in the pathogenicity of V. nashicola race 1 isolates when infecting cv. Kousui. For the second purpose, sequence variations of the endoPG gene from different pathological races were not race-specific, and these sequence variations could not be used for race identification. However, endoPG phylogeny supported the separation of V. nashicola from V. pirina, the cause of scab on European pear.