Effects Of Decapitation On Yield And Branch Growth In Brassica Napus L.

Brassica napus L.is one of the important oil crops,and the rape oil is an important part of edible vegetable oil in China.The ideal goal of the"used as vegetable and oil"planting mode is that the yield of the rapeseed will not decrease or even increase after the main stem or branches are removed in B.napus.Vigorously popularizing the"used as vegetable and oil"planting mode will effectively improve the economic benefits and initiative of rape growers,and it will play an important role in promoting the development of rape production and ensuring the safety of edible vegetable oil supply in China.In this experiment,first we studied the effects of decapitation on agronomic and yield traits of 20 B.napus cultivars?lines?,then selected A019 with a significant increase and A040 with no significant change in grain yield after decapitation,and analyzed the changes of auxin,cytokinin,gibberellin and soluble sugar contents in axillary buds and leaves at different nodes after decapitation.At the same time,we also analyzed the differential expression of BnaA01g26700D,BnaA03g34820D,BnaC01g34090D,BnaC05g51920D and BnaCnng23770D,members of BRC1 which can inhibit branching geowth,and discussed the effects of 6-BA and sucrose on axillary bud growth.And then to explore the preliminary regulation mechanism of branching growth of rapeseed after decapitation.The main results of this study are as follows:1.Decapitating could significantly reduce the plant height and branch position height,but had no significant effect on the number of primary branches and 1000-grain weight.Decapitating at appropriate time could significantly increase the number of branched pods and pods per plant,and increase the yield per plant in B.napus.2.The soluble sugar content in the upper axillary bud in B.napus was higher than that in the lower axillary bud at bud stage,and the soluble sugar content in the leaves was similar.The soluble sugar content of the leaves was reduced and the content of the anxillary buds was increased in 0¹ days after decapitation.3.Decapitating reduced IAA content at the tip of stem and broke the apical dominance of rapeseed plants,and increased IAA content in axillary buds at the top-down node,which formed a new auxin source in B.napus at bud stage.And decapitating increased IAA,ZR and GA₃ content in lower-part axillary buds which were dormant before,then the axillary buds activated and restored to the growth state.Decapitating also increased ZR and GA₃ content in axillary buds at the growth state,the axillary buds better formed primary branches,and supplementary branches which were removed.4.Five members of BRC1 gene of B.napus were analyzed for homology and phylogenetic tree construction.The homology with the amino acid sequence of BRC1gene of Arabidopsis thaliana was more than 70%.The genetic relationships respectively were BnaA03g34820D,BnaCnng23770D,BnaC05g51920D,BnaA01g26700D and BnaC01g34090D.The expression of BRC1 gene was low in axillary buds in B.napus at bud stage,and decreased after decapitation,indicating that decapitating reduced the expression of BRC1 gene and promoted axillary buds growth.5.External application of 6-BA could effectively promote axillary bud growth in B.napus at bud stage,and 0.10g/L 6-BA could make axillary bud grow continuously and bud appeared;the effect of decapitation and external application of suger were lower than that of 6-BA.