Peculiarities of downy mildew manifestation on sunflower at seeds inoculation by different races of pathogen before sowing

Peculiarities of downy mildew manifestation on sunflower plants in field conditions were studied after seeds separate artificial inoculation by P. halstedii races (330, 700, 710 и 730) before sowing. Race 330 depressed infected plants stronger then the other races. A lot of plants inoculated with race 710 carried a latent infection, and plants inoculated with races 700 and 730 had a longer vegetative and seed formation periods. The revealed features of races 700, 710 and 730 totally with a high virulence cause their wider spreading in future and can bring it to the leading position in structure of local P. halstedii population.