On the question about race structure of some broomrape (Orobanche cumana Wallr.) populations parasitizing on sunflower in Russia and Romania

Broomrape (Orobanche ситапа Wallr.), parasitizing on sunflower is one of the main factor limiting its production in the Russian Federation and in many other countries. A comparative analysis of race structure of O. umana populations from the south of Russia and Romania showed a big similarity of broomrape in both countries on a level of virulence. In some populations, broomrape overcomes action of dominant genes of resistance in sunflower ()r 5, Ore, Or7 and a joint action of two recessive genes or 6or?. A tendency of race G dominance in parasite populations is observed. Races incapable to overcome action of above-noted genes of sunflower were eliminated in many populations. Herewith, in both countries there are populations with a less virulence where gen Or? and joint action of genes or 6or? of sunflower work effectively. Inhomogeneity of race G on virulence is revealed: in both countries there are populations both overcoming only resistance controlling with gene Or 6 and all previous genes, and overcoming the joint action of two recessive genes oreor 7. It is concluded that overcoming of action of genes or 6or? is not connected with impact of environments and presence in population units able to overcome sunflower resistance connected with a gene Or?.