Occurrence and Distribution of Races 713, 733 and 734 of Sunflower Downy Mildew Pathogen in the Russian Federation

Abstract The samples of Plasmopara halstedii (the causal agent of sunflower downy mildew) were collected on sunflower fields in south of the Russian Federation: in the Krasnodar, Rostov and Stavropol regions, and in the Republic of Adygea in 2016 and 2017. Virulence code of 545 isolates was identified; i. e. 280 isolates originating from 24 fields in 2016, and 265 isolates from 17 fields in 2017. Races 330, 334, 710 and 730, widespread within the region in previous years, were found in all mentioned areas. In addition, races 713, 733 and 734 have been detected in several districts of the Krasnodar region since 2016. This is the first report of these races in Russia and above that the first record throughout Europe and Asia for the races 733 and 734. The identification of new P. halstedii races was confirmed by the method of cross inoculations from individual differential lines. The phenotype corresponding to virulence code 734 was in some cases disclosed as a mixture of race 334 with 710 or 730. The presence of several P. halstedii races on an individual plant was also confirmed for the first time in the territory of the Russian Federation.