The diseases on sunflower are a limiting factor for sunflower production not only in Bulgaria but also in all countries where the crop is grown. This is the reason for the great number of researchers who have directed their efforts toward solving the problem. A priority in the research work carried out at DAI is the problem not only of seed quality and quantity, but also the phyto sanitary condition of sunflower. The results from the past ten years and more show that success has been achieved in the resistance to leaf fungal pathogens (Phomopsis helianthi; Phoma macdonaldi; Alter nar ia sp.), downy mildew (Plasmopara halstedii) and the parasite broomrape (Orobanche сumana). The result from the activity of the researchers working at DAI are the released hybrids San Luka, Mousala, Mercuriy, Maritsa, Mesta, Moura, Magoura, Biotsvet, Rada, Yana, Valin, Dobrotsvet, Alpin, Mihaela, Vokil, Veleka, Velko, Gabi, etc. A part of these hybrids were developed by conventional methods, others - by using bio technology methods, while the development of third hybrids involved a combination of both. Many of them are now in production demonstrating good results, and others are to be approved by the national agencies. Each of these hybrids possesses complex resistance to some of the leaf fungal pathogens, as well as obligatory resistance to downy mildew and broomrape. The genetic stock center of DAI maintains a great number of lines derived mainly from the wild annual and perennial species. They are used as donors of resistance in the breeding program of the institute