Contamination of Wheat Seeds with Parastagonospora nodorum Berc
The purpose of the study was to improve the analytical method to identify the seed contamination level with the pathogen Parastagonospora nodorum in large-scale phytosanitary monitoring. An analysis of 179 spring seeds samples and 24 winter wheat samples showed that the seeds infection rate with P. nodorum varied from 0.6-4.2% (Altai Krai, Tyumen region) to 1.7-15.0% (Novosibirsk and Tomsk regions). The excess over the economic threshold of harmfulness in some years reached 4.4-7.1 times, and for 26% of lots in the wet years, the infection rate of Septoria blight was the criterion for the choice of protectant. Freshly harvested winter wheat seeds were infected with the Septoria blight pathogen more than spring wheat seeds. The study of varieties from three Siberia regions in the epiphytotic year made it possible to identify the following trend: the distribution of Septoria agent occurred more actively with seeds of varieties of Novosibirsk selection in comparison with the Omsk and Kurgan regions. Seed protectants regardless of their action mechanism (contact, systemic) and the active ingredient showed high laboratory efficacy against P. nodorum, which was 80.4-96.1%. A protectant with the prolonged action reduced the Septoria blight development at the flag leave and on the ear 1.5-2.0 times under field conditions. The assessment of the effectiveness of an integrated protection complex at pre-sowing preparation of seeds of two wheat varieties showed, that a combination of calibration, pre-sowing heating and treatment increased seed germination by 6% and reduced the contamination with P. nodorum by 92.9% compared with the baseline.