To the question of Phomamacdonaldii (Boerema) harmfulness on sunflower

The experiment allowed establishing the sunflower plants can be infected by Phoma pathogen at the first stages of plant development through close contact of root with infected plant residues and seeds. The main symptoms of infection were as follows: delay in plants growing and development, black necrosis spot on root collar often spreading on hypocotyl or cotyledonary leaves, surrounding black necrosis spot on main root or hypocotyl. We united the similar symptoms into four groups on an infection level. We determined Phoma harmfulness by fourth infection group (plants death in an emergence phase and unviable seedlings with black necrosis spot on hypocotyl and cotyledonary leaves). Such account of root infection showed Phoma harmfulness for a sunflower line VK 653 was 66%, for a hybrid Altair - 53%.