Studies On Genetic Analysis And The Regulation Of Application Of Fertilizers On Waterlogging Tolerance In Rapeseed (brassica Napus L.)

In China, over 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 waterlogging tolerance of Zhongshuang 9×GH01 was dominated by two pair 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 (h2mg) in F2 population was 73.57%, it suggested that it will be effective way for waterlogging tolerance breeding to select at early generations.The rapeseed (Brassica napus L.) varieties of Zhongshuang 10 and Zhongyouza 5 were taken to test the flood tolerance on the seedling stage to simulate the waterlogging stress. We used the"3414"fertilizer effect experiment for studying the effects of application of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on yield in rapeseed under the waterlogging stress. The results showed that nitrogen, phosphorus and potassium have an significant effect on yield traits in rapeseed under the waterlogging stress. The grey relational analysis showed that the N application was significantly related with the number of seed per pod, the number of siliques per plant, the number of primary branches, the number of secondary branches and the length of raceme. The P application was significantly related with the number of siliques per plant and the number of seed per pod. And the K application was tend to significantly related with the number of seed per pod, 1000-seed weight, the length of raceme. The results indicated that the middle level of phosphorus and potassium fertilizer, increased use of nitrogen fertilizer can significantly increase the yield of rapeseed and the cost value ratio and economic benefits in the paddy field with excessive soil moisture. By establishing the fertilizer response equations, the optimum fertilizer applicant of rapeseed under the waterlogging stress were as N: 267 kg/ha, P2O5: 120 kg/ha, K₂O: 120 kg/ha.