The situation in the population of the sunflower downy mildew pathogen in some regions of the Russian Federation

Abstract

Downy mildew is one of the most spread and harmful diseases of sunflower (Helianthus annuus L.). The aim of the study was to determine the races of the pathogen of the disease of the oomycete Plasmopara halstedii (Farl.) Berl. et de Toni in several regions of the Russian Federation (the Republic of Adygeya, Krasnodar Krai, Stavropol Territory, Volgograd, Lipetsk, Saratov and Rostov regions) and the sensitivity of its isolates to the fungicide mefenoxam. The races were determined using an international standard set of nine sunflower differential lines carrying different genes of resistance to P. halstedii (genes are named Pl). In total, over all the years of research (more than 30 years), 11 P. halstedii races were identified in Russia; the most common of these in recent years have been races 330, 334, 710 and 730. Sunflower lines HA-337, Rha-340 and Rha-419 have also been tested for resistance to the identified races. Sunflower lines 803-1 (Pl5+), Rha-340 (Pl8) and Rha-419 (Plarg) were resistant to all P. halstedii races that have been found in the regions of the Russian Federation. The sensitivity of the pathogen isolates to the fungicide mefenoxam was determined by a laboratory method using sunflower seeds of the universally susceptible to downy mildew VNIIMK 8883 variety treated with the preparation Apron XL, FS (mefenoxam 350 g/l, Syngenta, Switzerland) in accordance with the recommended in the Russian Federation dose (3 l/t of seeds). Mefenoxam-resistant isolates of P. halstedii have been found in the Krasnodar Krai. To protect sunflower crops from downy mildew, it is necessary to select and cultivate genotypes with resistance to the complex of P. halstedii races.