IndentiHcation Of Races Of Plasmodiophora Brassicae And Resistance To Clubroot In Rapeseed

At present, the clubroot caused by the soil-borne obligate parasite Plasmodiophora brassicae occursin more than60countries, leading to crucifer crops production losses of10-15%per year around theworld. In China, the disease was first identified on cruciferous vegetables and caused great economiclosses and later spread to the oilseed rape. The disease on oilseed rape had rapidly spread in Yunnan,Sichuan, Yichang in Hubei Province, Huangshan in Anhui Province, and other places. In this study,optimization of the purification methods of resting spores，identification of physiological races of thepathogenon oilseed rape，physiological races distribution，and screening resistant rape variety todifferent physiological races were finished. Results of the study are as follows:The resting spores were separated from rape clubroot from Hubei ZhiJiang using the NaClO andsucrose suspension methods respectively. The results showed that the concentration of resting spores insuspension was not significantly difference between two methods, but the impurity substance of sporesuspension prepared using sucrose suspension method was less. The susceptible chinese cabbage showheavy infections with resting spore suspension prepared using sucrose suspension methods. The bestapproach for preparation of the spore suspension for different uses was established through optimizationof centrifugal force, time and times of sucrose suspension method.Williams system was used to identify main physiological races of Plasmodiophora brassicae, thepathogen of oilseed rape (Brassica napus L.) clubroot from19main disease regions. Results indicatedthat at least3races (as Race2,4and13) existed in China. Race4was dominant from16locations,including Zhijiang and Dangyang of Hubei Province, She County of Anhui Province,4counties ofYunnan Province,5counties of Sichuan Province. Race13and2distributed in Qiyunshan Town andShangshan Town of Anhui Province, respectively.The Resistance of214oilseed varieties to clubroot disease (P. brassicae) was evaluated under fieldconditions in Zhijiang and Huangshan. According to the disease index Brassica napus cv. Ganliangyou3,Rongyou9, Zheshuang6, Huayouza12, Zhongyouza8, Zheshuang8, Zhongyou5628, Yangyou8,Ningyou12, Zheyou28, Zhongshuang10and Fengyou520were classified into resistance to Race No.4in Zhijiang. The Chengyouza6, De68-12and Chuzayou3were resistant to Race No.13in Huangshan.These varieties could serve as resistant breeding parents and commercial variety in the distributionregions of corresponding clubroot race.