Comparability of results from evaluating sunflower lines resistance to Phoma black stem infection under natural and artificial conditions

The phytopathogenic phomoid species Plenodomus lindquistii (Frezzi) Gruyter, Aveskamp & Verkley is the pathogen of black stem, a widespread sunflower disease in Russia. An effective, environmentally safe strategy for controlling this disease is to develop resistant genotypes, which is one of the important areas of sunflower breeding. This study aims to compare the degree to which sunflower line material is affected by Phoma black stem under natural and artificial infection. From 2022 to 2024, we monitored constant sunflower parent lines for resistance to disease during the flowering and maturing stages at the field experimental base. In the field experiment, lines L 687 and L 700 were the most affected by Phoma black stem over three years, with prevalence (P) ranging from 32.9% to 7.5% and 33.8% to 7.8%, respectively, and development (R) ranging from 15.8% to 2.1% and 18.9% to 2.0%, respectively. Over three years, lines VK 595, VK 5951, L 696, and L 64515 exhibited partial field resistance, with prevalence ranging from 0% to 6.6% and development ranging from 0% to 2.3%, respectively. To make a comparison, a vegetation test was involving the artificial inoculation of sunflower lines with pycnidia from the anamorphic stage of the pathogen P. lindquistii. The results of the sunflower plant infection with Phoma black stem in the conditions of the vegetation test and field evaluation were comparable in terms of the reaction of the studied genotypes, with the exception of line VK595. Three promising mediumresistant lines (VK 5951; L 696; L 64515), five susceptible (VK303; L 665; L 64215; L 63415; L 62215) and two highly susceptible (L 700; L 687) lines were identified.