Technology for the accelerated assessment of the resistance of sunflower breeding material to the rust pathogen Puccinia helianthi Schwein

The coevolution of the sunflower host plant and the rust pathogen Puccinia helianthi Schwein. requires constant monitoring of parasite virulence and continuous selection for host immunity. After discovering new virulent biotypes of the parasite in the sowings across Russia from 2018 to 2024, the authors developed technology for accelerated assessment of sunflower breeding material's resistance to the rust pathogen. One element of this technology is a method for obtaining and propagating clones of urediniospores of a specific virulence to infect evaluated sunflower samples. The spores of the desired virulence are isolated and propagated on the cotyledon leaves of sunflower seedlings. To evaluate the breeding material, the seedlings are grown in plastic germinating dishes on a moist mineral wool substrate under controlled temperature and lighting conditions for nine to ten days. The cotyledon leaves of fivedayold seedlings of studied sunflower genotypes are infected. For their artificial infection, the optimal concentration of spores in the inoculum and the necessary volume for infecting 110 seedlings were selected and justified. The degree of plant infection is assessed using a scale developed by the authors. A comparative analysis of the degree of infection of 20 sunflower genotypes was performed using a biotype with a virulence code number 700, comparing the technology developed by the authors with an existing technology. In the latter, the second pair of true leaves of 14dayold plants grown in soil were infected. The reliable comparability of the assessment results obtained using both technologies, in terms of both the degree of infection and the type of reaction, is confirmed mathematically at a 5% significance level. In addition to reducing the assessment period by nine days, the proposed technology eliminates the need to grow sunflower plants in soil for infection. This enables the assessment of a significantly larger number of breeding material samples in an artificial climate chamber.