Abstract:

One doubled haploid (DH) population derived form F1 plants of the cross between DH401 (P₁) and Q2 (P₂) was used to study the inheritance of flowering time and photoperiod sensitivity of spring Brassica napus in this study. Two parents had exhibited a low and high sensitivity to photoperiod, respectively. Days to flower (DTF) were investigated in the P₁, P₂ and DH population at Hezheng (Gansu Province) with a long day in summer and at both Zhaoqing (Guangdong Province) and Wuhan (Hubei Province) with a short day in winter for consecutive two years. Photoperiod sensitivity index (PSI) was calculated according to DTF obtained from Hezheng and Zhaoqing. The means of DTF and PSI were analyzed by applying a mixed major gene and polygene inheritance model. The results showed that DTF at Hezheng, Wuhan and Zhaoqing was controlled by 3, 2, and 2 pairs of major genes with additive and epistatic effect plus polygenes, duplicate effect plus polygene, respectively. Heritability values of the major genes at the three locations were 91.13%, 63.05% and 62.02%, and those of polygenes were 4.43%, 1.58%, and 22.71%, respectively. The PSI was conditioned by 2 pairs of major genes with epistatic recessiveness effect and some polygenes. The heritability values of the major genes and polygenes were 50% and 37.5%, respectively. Other genetic parameters were also estimated. Therefore, it is speculated that both flowering time and photoperiod sensitivity in this DH population were controlled by 2 or over 2 pairs of major genes and polygenes, and the plants might have some different interaction models among flowering genes under different photoperiods. Meanwhile, how to use the results for Brassica napus breeding was discussed.

Key words: B. napus L., Flowering time, Photoperiod sensitivity, Mixed major gene and polygene inheritance model, Genetic analysis