Resistance of new sunflower hybrids to sunflower broomrape (Orobanche cumana) and the possibility of their use in the strategy of protection against the parasite

Sunflower broomrape ( Orobanche cumana Wallr., 1825) is a significant and challenging parasite in sunflower crops gl o bally, infesting approximately 16 million hectares. Annual global crop losses due to broomrape infestation reach about 2.3 billion EUR. Therefore, our work addresses the critical scientific task of determining the spread, harmfulness, and racial composition of broomrape, developing protective measures for sunflowers against this parasite,and assessing the resistance of sunflower hybrids to broomrape. A pot experiment was conducted to identify the racial composition of the parasite and the resistance of various sunflower hybrids. Sunflower hybrids were evaluated for resistance to broomrape in soil culture using a modified method and the roll method of seed germination. Broomrape is actively spreading from the northern steppe of Ukraine to the country's central, northern, and western regions. The sunflower hybrids ES Nirvana, ES Romantic, ES Genesis, ES Bella, ES Andromeda, Janis, ES Niagara, and ES Artik, which are tolerant to race G, showed some parasitic effects from broomrape, though the degree of damage was not severe. On average, each sunflower plant had 2 to 3 nodules of the parasite. No sunflower hybrids exhibiting complete immunity to broomrape were discovered. Since sunflower hybrids ES Nirvana, ES Romantic, ES Genesis, ES Bella, ES Andromeda, ES Janis, ES Niagara, and ES Artik, resistant to race G, were affected, broomrape races A-F (race 6) significantly infest sunflower crops. Sunflower hybrids resistant to broomrape race E should not be cultivated, as this may lead to further spread of the parasite and a reduction in yield. Due to the minimal damage to the su n flower hybrids resistant to race G, race H (race 8) has recently begun to emerge in sunflower crops. Research to identify these more aggressive (H and I) races of the parasite is hindered by the lack of differentiating lines of sunflower resistance and hyb r ids for identification. Unfortunately, no hybrids resistant to race H (race 8) exist. The best sunflower hybrids show resistance to race G (race 7). The differentiation of sunflower hybrids grown for resistance to this parasite was completed. It has been noted that the broomrape population displays a considerable level of virulence that can overcome the immunity present in the most resilient foreign-bred hybrids resistant to races E, F, and G of the parasite. The widespread accumulation of parasite races E, F, G, and H in sunflower crops is connected to the disruption of crop rotations and the excessive cultivation of hybrids of this crop, primarily resistant to races 5 (E) and 6 (F) of the parasite. The research findings can be applied in the region's farms for effective prote c tion against broomrape and in breeding programs aimed at creating sunflower hybrids resistant to new parasite races, as well as corn hybrids that enhance seed germination of this pathogen in the soil and promote their death through root secretions.