The Genetic Population Structure of Pyrenopeziza betulicola, the Causative Agent of Birch Leaf Spot Disease

Abstract

Pyrenopeziza betulicola is a causative agent of leaf spot disease on birch. Within P. betulicola sig- nificant length variation (nine alleles) in 18S ribo- somal genes was observed. The level of geographic differentiation among all locations was moderate but statistically significant, indicating that the spore dis- persal of P betulicola occurs mainly on a limited scale. Within one leaf, in situ analysis of a multiallelic mo- lecular marker revealed genetically distinct individu- als in different spots, indicating that multiple colo- nization by P betulicola is a common occurrence on birch leaves. Within one spot only one allele was found showing that the separate necrotic spots are usually formed by only one viable spore. Technically, the application of a specific marker combined with DGGE turned out to be a powerful method to study