Creation Of Dwarf Brassica Napus Germplasm Resistant To Clubroot

Rapeseed is the most important oil crop for domestic vegetable oil,ensuring the safe production of rapeseed is essential for strategic security of edible oil in China.In order to increase efficiency and field production,the mechanization of rapeseed industry requires good variaries that are suitable for high density cultivation.China’s rapeseed industry is threatened by clubroot disease,the use of chemical and physical means to control clubroot has limited effect and are also costly,therefore breeding and cultivation of clubroot-resistant varieties is considered the most cost-effective solution.At present,the majority of Brassica napus planted in China are high-stem-loose plant type,which has weak lodging resistance and therefore unsuitable for mechanized harvesting.Rapeseed lodging will cause stacking between plants,reduction on absorption of light will seriously affect the quality of rapeseed.Therefore,clubroot resistant,dwarf-stem-compact varieties has become two important objectives for rapeseed breeding.Based on the germplasm resources created previously in our laboratory,we aim to improve the plant type of ZS11R by using three dwarf materials（XNAG,F-Dwarf and DW871）.We screened progeny plants by field phenotypic measurement and molecular marker selection,we used NIRS and clubroot in-house inoculation to create high-quality clubroot resistant dwarf rapeseed materials.The main findings in this study are as follows:1.Architecture improvement of ZS11R using XNAG of ZS11 background to create clubroot resistant dwarf rape germplasm resources.Progeny plants with dwarf-stem phenotype and homozygous CRb locus for disease resistance markers were selected in the F₂generation.Plants with dwarf-stem and homozygous state for resistance genes were selected for selfing,and the F₃generation with excellent quality was created,which met the standard of"double low"rape.Among these,the field phenotype of the F₃generation from 21WHS004-160 selfing was relatively neat,the plant height was similar to XNAG,the CRb locus are all homozygous,the resistance to Zhijiang Plasmodiophora brassicae reached a high level of resistance.2.We used the compact F-Dwarf to improve the plant architecture improvement of ZS11R to create compact rapeseed germplasm resource with resistance to clubroot.By combining the results of molecular marker-assisted selection with field phenotypic identification and quality analysis,we selected homozygous CRb locus dwarf compact plants in BC₂F₁generation for self-crossing and backcrossing,and created high generation material with good quality,which met the standard of"double low"oilseed rape.The plant height of the BC₃F₁generation of dwarf compact material planted in Gansu Hezheng was 70.14%of that of ZS11R,and the average branching angle was 49.82%of that of ZS11R.The indoor inoculation results showed that both BC₃F₁and BC₄F₁generation materials were highly resistant to Zhijiang Plasmodiophora brassicae.3.Plant architecture improvement of ZS11R using DW871 to create clubroot-resistant dwarf compact rapeseed germplasm resource.In this study,we used molecular marker-assisted selection combined with field phenotypic identification to select homozygous CRb locus dwarf compact plants for self-crossing and backcrossing,and used NIRS to screen the obtained progeny populations to select high generation materials that meet the standard of"double low"oilseed rape.The dwarf compact material of BC₃F₁grown in Gansu Hezheng had 69.36%of the height of ZS11R and 47.74%of the average branching angle of ZS11R.Both BC₃F₁and BC₄F₁generation materials in the improved progeny population reached a high level of resistance to Zhijiang Plasmodiophora brassicae.