Intergeneric Crosses For The Transfer Of Resisitance To The Clubroot From Raphanus Sativus To Brassica Napus

Clubroot is a worldwide soil-borne disease of cruciferous plants infested by Plasmodiophora brassicae Woronin.At present,it has spread to many major areas of rapeseed production,and has become one of the main diseases affecting the yield and quality of rapeseed in China.Breeding and cultivation of disease-resistant varieties is currently recognized as the safest and most effective method.However,the resistance resources of the Brassica napus L.are scarce.It is of great significance to mine disease-resistant resources and broaden the genetic basis of rapeseed resistance to ensure the safety of rapeseed production in China.Interspecific hybridization is an important means to broaden the genetic basis of cruciferous crop.The studies on the cross progeny of radish and rape with anti-root disease are fewer.In the previous study,nine radish varieties were identified to be resistant to the P.brassicae isolates collected from clubroot-infested field plots in Zhi'jiang,and then they were used as a male parent to hybridize with the susceptible Brassica napus"411"to transfer clubroot disease resistance.Results of the study are as follows:1.The clubroot disease resistance of 20 radish varieties to P.brassicae isolates which were collected from 9 regions of China was identified.Among them,Jingyanyeyong was immune to all of the P.brassicae isolates;Hongliandan and Hetiansanjimeihua showed high resistance to all of the P.brassicae isolates;Taiwanese varieties Niupuyi,Jimeihongpi and Chunlu were susceptible to PbES;Xinmeixinyingtao and Taiwanese variety Hongjiyingtao radish were susceptible to PbES and PbHS;Hongxinhongpi was susceptible to PbES,PbHS and PbPX;none of the remaining 11 radish varieties were resistant to all of the P.brassicae isolates.2.The nine clubroot resisitance radishes were crossed with susceptible rapeseed.Of the 9 cross combinations,two cross combinations produced F₁ plants.By flow cytometry,radish specific labeling and chromosome number observation,the results of the three methods consistently confirmed that there were only two true hybrids in the combination of"411×Jingyanyeyong".They were obtained under ovary culture and natural conditions,respectively.3.True hybrid stamens were aborted and had no pollen.After treatment with colchicine,the pollen fertility reached 35%,and the pistil showed that the plants contained 56 chromosomes,indicating that the hexaploid plants were successfully obtained,ie,the S₀ generation.4.The S₀ plants were used as the female parent to backcross the Brassica napus L.,and a total of178 seedlings were obtained.According to the test of disease resistance,171 showed resistance to disease,and 7 were grade III susceptible;most resistant plants contained 47 chromosomes,but found that a disease-resistant plant with yellow flowers contained 43 chromosomes.5.Phenotypic observation and analysis of F₁ and BC₁ plants of true hybrids showed that the phenotype of true hybrids was between parents,and vegetative growth was much more vigorous than reproductive growth.The leaf shape of the BC₁ generation is similar to that of rapeseed,and the shape of the flower is smaller than that of the female parent,and the color of the flower is white.Successfully doubled plants had large and plump flowers,together with blur on the blade edge.The length of the back-crossing podswas similar to that of the rape pods.The ratio of fruit body to fruit beak was similar to that of radish pods,which was 1:1.The BC₁ generation showed obvious morphological separation.In the seedling stage,some plants had main stems,similar to Brassica napus,while some had no main stems together with scattered branches and leaves,similar to radish.The difference in leaf shape is mainly manifested in the leaf margin,from zigzag to ellipse.Most of the flowers were white in color,and only one individual plant returned to yellow.