Reaction of sunflower genotypes to Sclerotinia sclerotiorum under greenhouse conditions
Siamak Rahmanpour Ozan; Mehdi Ghaffari and Nadia Safavi Fard
Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.
Sclerotinia sclerotiorum attacks many dicot plants including oilseed rape, soybean, tobacco and sunflower worldwide. The disease stem rot of sunflower caused by the fungal pathogen in Iran is one of the most destructive diseases and causes economic yield lost annually, in particular North West of Iran. Despite lack of resistance to the disease, the different genotypes demonstrate different reactions against the disease. To evaluate the reaction of oilseed sunflower restorer lines, 3-week-old plants grown and incubated in greenhouse, were inoculated employing mycelia discs of the fungal pathogen. The sclerotia of the fungus were collected from Khoy area located in North West of Iran. A single sclerotium was cultured and mass-produced on potato dextrose agar medium. Then three-day-old mycelium plugs with 7 millimeter diameter were used for inoculation. The symptoms of the disease including cotyledon infection and necrosis, stem infection and necrosis, and damping-off were measured and scored 1, 2, and 3 based on disease progress, respectively. A majority of inoculated plants were scored three, based on sever damping-off. The effect of disease was significant on the genotypes and all 21 restorer lines demonstrated susceptibility to the pathogen.
Keywords: sunflower, stem rot, inoculation, mycelium plugs.