Pathotypes of sunflower downy mildew in southern parts of Germany.
During the past six years the occurrence of Plasmopara halstedii and the regional distribution of its pathotypes in the southern parts of Germany was investigated. More than 50 isolates, representing fields of all regions relevant for sunflower production in the State of Baden-Württemberg, two areas in Bayern and one locality in Hessen were collected. Pathotype characterization, based on sunflower differential lines and evaluated according to a triplet code system, indicated the existence of at least five pathotypes. Among them, pathotype 730 (former race 4) dominated by far, frequently accompanied by 710 (former race 8), while pathotypes 330 (former race 7 or 9), 310 (former race 6) and 300 (former race 2) were only sporadically present. Studies on single spore isolates selected from certain field samples mostly documented the existence of more than one pathotype per field.