RESISTANCE OF SUNFLOWER BREEDING MATERIAL TO PHOMOSIS DAMAGE

Abstract

The comparative study of sunflower constant lines resistance to Phoma rot using different methods of artificial inoculation with the disease pathogen was conducted. The most aggressive isolate of the Phoma rot pathogen Plenodomus lindquistii was used for inoculation. It was isolated from the stem of the affected sunflower plant in the breeding nursery of V.S. Pustovoit All-Russian Research Institute of Oil Crops. In a greenhouse conditions, there were used two methods of artificial inoculation with a fungus at bottom of the leaf petiole of sunflower plants at the stage of the first pair of true leaves. In the first case agar pieces with mycelium, pycnidia, and picnospores were applied; in the second one 0.2 ml of the suspension of fungal spores was introduced by syringe injection. In the two control variants, plants were injected with sterile water, or pieces of sterile agar nutrient medium OA (oatmeal agar) were applied to them. The number of replications was four (10 plants each). The plants were cultivated at a variable temperature of 25-30 oС during the day and 25 оС at night (16-hour photoperiod). The cultivation duration was until the budding stage, and we recorded the affection on the 30th day after the start of inoculation. The intensity of the Phoma rot development was determined using a five-point immunological scale. The first method of inoculation (without injury) revealed resistant (VK 900, L 86) and mid-resistant (L 107, L 132) sunflower lines. The second method identified five susceptible (L 2385, L 103, L 136, L 131, L 128) and one highly susceptible (L 82) sunflower lines. In laboratory, the inoculation of the roots of sunflower seedlings by the quick test revealed two constant lines L 116 and L 136 with more than 50 % of plants with healthy root systems or with a small affection degree (1 point). Lines L 2385, L 103, L 131, and L 120 showed the largest number of plants with a medium degree of root affection (2 and 3 points). The resistance of stem and roots to Phoma rot affection in different sunflower lines was manifested both in combination and separately, which should be taken into consideration when selecting genotypes resistant to Phoma rot.