Abstract: Rapeseed is one of the most important oil crops in the world. Lodging damage results in not only lower seed yield and oil quality, but also easier infection to the infection of Sclerotinia and more difficulties for mechanized harvest. So it is of a great significance to study lodging resistance in B. napus L. However, lodging is a complex trait associated with several factors. It is difficult to evaluate in field. In this paper, inheritance of lodging resistance was analyzed applying the joint segregation analysis of a mixed genetic model of major gene plus polygene in six generations (P1, P2, F1, B1, B2, and F2 ) derived from two crosses of Zheping 1 (lodging resistance) × 04Pb11 (lodging) (Cross I) and Ning 1243 (lodging resistance) × 04Pb11 (Cross II) in B. napus L. Resistant pressure per plant (RPPP) was measured at flowering time by Digital Force Gauge, which was used to assess the ability of lodging resistance, and the correlation between RPPP and lodging scale was scored at mature time (r = -0.38, P≤0.01). The results showed that lodging resistance was dominated by two major genes with additive-dominance-epistatic effects plus polygenes with additive-dominance-epistatic effects (E-0 model) in Cross I, and two major genes with additive-dominance-epistatic effects plus polygenes with additive-dominance effects (E-1 model) in Cross II. The additive effects of two major genes in two crosses were more powerful than the dominant one (︱h/d︱＜1). On average, Hereditability of major genes (hmg2) was 54.71% in F2 population, and that of polygenes (hpg2) only detected in B1 population was 10.56%. It indicated that the lodging resistance in B. napus L. was dominated by major genes. In addition, the environmental variance and the genetic variance accounted for 46.57% and 53.43% of the phenotypic variance in each population respectively, indicating that the environmental factors have a great effect on lodging in B. napus L.. However, higher hereditability of major genes can be favorable to an efficient selection in early generation of lodging resistance breeding.

Key words: Brassica napus L., Major gene plus polygene model, Lodging resistance, Genetic analysis