Genetic analysis of waterlogging tolerance for germinated seeds of rapeseed (Brassica napus L.) with mixed model of major gene plus polygene.

In China,more than 85%of the rapeseed production is from the Yangtze River Basin.Rapeseed planted as rotation crop following rice from autumn to beginning of the second year summer,often encounters waterlogging stress because of enduring rainfall in autumn and humid paddy soil,which results in reduced field emergence and weaker seedlings.To reveal the genetic mechanism of waterlogging tolerance in rapeseed,we studied a genetic system of waterlogging tolerance in rapeseed by means of a joint segregation analysis in the multi-family generations(P1,F1,P2,B1,B2,and F2)derived from a cross of Zhongshuang 9×GH01.The results showed that the waterlogging tolerance of Zhongshuang 9×GH01 was dominated by two pairs of major genes with complete dominance effects plus polygenes with additive-dominance effects(E-5 model).Additive effect(d=0.0696) was equal to dominance effect(h=0.0696)in the first major gene,and also the additive effect(d=0.0530)was equal to dominance effect(h=0.0530)in the second major gene of the genetic system.Effect of polygenes acted in the manner of additive([d]=0.3275) as well as dominant with a negative value([h]=–0.2137).It indicated that there was heterosis for waterlogging tolerance found in the cross that played an important role in the genetic system of waterlogging tolerance.Heritability of major gene(h2 mg )in F2 population was 73.57%,which suggested that seletion in early generations will be effective way for waterlogging tolerance breeding.