Expression of heterosis in economically important traits in hybrids of spring rapeseed (Brassica napus L.) developed using the CMS Polima

Abstract

This article presents the results of a comprehensive assessment of the manifestation of true and competitive heterosis in spring rapeseed (Brassica napus L.) hybrids that were developed using the Polima cytoplasmic male sterility system. The studies were conducted under the forest-steppe conditions of the Central Chernozem region of Russia in 2024–2025. The study subjects included F1 hybrids, sterile maternal lines with the Polima CMS system, fertility restorer lines (Rf lines), and the standard variety Ratnik. The evaluation was based on key economically important traits that determine seed productivity and biochemical seed characteristics, such as the pod number per plant, seed weight per plant, oil content, and protein content. The manifestation of heterosis was found to vary depending on the hybrid combination and trait analyzed. The LHS-1 × HYFR-2 (S2) hybrid exhibited the most pronounced positive true and competitive heterosis in terms of pod number and seed weight per plant, with true heterosis values reaching 30.5–32.5%. The degree of phenotypic dominance indicated superdominance of the traits. In terms of oil content, this hybrid also outperformed the parent lines, reaching 44.3%. The maximum protein content (up to 29.1%) was observed in the Sample No. 5 × HYFR-2 (S2) hybrid combination. These results demonstrate the potential for using the Polima CMS system in developing spring rapeseed hybrids and for identifying parent material for further breeding work.