Effect of the duration of growing season on spring rapeseed yield in the conditions of Western Siberia

The article presents the results of field studies of spring rapeseed samples with different photoperiodic sensitivity, conducted in 2023–2025 under the conditions of the southern forest‑steppe of Western Siberia (Omsk Oblast) on chernozem soils. The aim of the research is to develop highly productive, early‑maturing, mid‑early and mid‑maturing varieties of spring rapeseed adapted to the conditions of Western Siberia, based on the principle of selecting the source material. To create new samples, VIR collection material and variety samples from scientific institutions of domestic and foreign origin were used, with hybridization and individual selection applied. The studies revealed that contrasting weather conditions prevailed during the years of the study, which affected the yield data. The hydrothermal coefficient (according to Selyaninov) was as follows: 0.50 in 2023, 1.40 in 2024, and 1.46 units in 2025. The studied samples were divided into 4 ripeness groups: early-maturing (80–85 days), mid-early (86–89 days), mid-season (90–95 days), and late-maturing (96–99 days). Among the studied samples, the largest percentage — 30.0% — was made up of mid-early samples, with a growing season of 86–89 days, and mid-season samples accounted for 47.5%, with a growing season of 90–95 days, respectively. Based on the results of three years of testing, two promising breeding numbers were identified: 29658 and 31356, which belong to the mid‑early group and have seed yields of 2.54 and 2.61 t/ha, respectively, which is 0.21 and 0.28 t/ha higher than the standard. In the mid‑season group, number 32683 (variety Azart) stood out, with a maximum seed yield of 2.73 t/ha.