Building Differential Hosts System For Plasmodiophora Brassicae Wor. In China And Identification Of The Physiological Races

Plasmodiophora brassicae Woron.is the pathogenic that causes the clubroot.Clubroot is a worldwide disease that is harmful to the root of cruciferous plants.The practice proved that planting blast resistance cultivars is an economical and effective way to control the disease.The identification of physiological races is directly related to the eddective breeding for clubroot-resitant crops,because of existing differentiation of physiological races in P.brassicae.Proved the distribution and advantage of pathogenic races is a basic work in our country,which is important for the prevention and control of the clubroot disease.At present,Williams hosts system or ECD system are widely used at home and abroad.However,the two identification systems have their limitations in China.First of all,the total hosts belong to cold varieties,which are difficult to breed in southern China.Secondly,the general disease identification systems is better for European strains,while the differentiation of Asian strains appear insufficient.Thirdly,these hosts are unable to accommodate the environment in many parts of China,the growth is weak,which affects the identification results to some extent.Therefore,on the basis of the natural science foundation project?differential hosts system of clubroot and the molecular identification?,this study is committed to establish a new differential hosts system,then identify the physiological races,which can make up for the inadequacy of international general system used in China.The results of the study are as follows:1.Building "0,1" differential hosts system and identify the physiological races in ChinaAccording to the early stage of the study,9 compatible Brassica plants and 15 regions of the clubroot materials in this country have been Collected.The resistance response of the hosts was obtained through the laboratory inoculation test.According to whether symptoms showed on the hosts after inoculation,four varieties N105-3,B-CL,B-CF,B-HT were selected from the primary screening hosts,who have difference in "quality".These varieties form the "0,1" differential hosts system."0,1" hosts system can separate 8 different physiological races from 42 regions of the clubroot strains in 12 provinces of China.Compared with Williams host system,"0,1" hosts system has the following advantages:standard is clearer,the error is smaller and can obtain massive seeds for the total hosts.2.Building "threshold" differential hosts system and identify the physiological races in chinaAccording to the early stage of the study,10 compatible Brassica plants and 11 regions of the clubroot materials in this country have been Collected.The resistance response of the hosts was obtained through the laboratory inoculation test.It is using a disease index as a threshold,namely the difference on the "amount".This system using DI = 30 as threshold,?30 is susceptible,< 30 for disease resistance.Three varieties G-11?B-908?B-CHJ were selected from the primary screening hosts,who have difference in amount forming the "threshold" differential hosts system."Threshold" hosts system can separate 5 different physiological races from 34 regions of the clubroot strains in 12 provinces of China.Compared with Williams host system,"Threshold" hosts system has the following advantages:easy to operationd and the hosts are easy to breed.3.Identify the physiological races by Williams host system in chinaWilliams hosts system can separate 6 different physiological races from 52 regions of the clubroot strains in 12 provinces of China,and the races number in Sichuan province is largest.For never identificated clubroot materials from hebei tangshan,Williams hosts system separate it in 4 race who has the strong pathogenicity.Classify the clubroot strains from Mianyang,Ningguo and Jixi as a new physiological races in number 4.Discover 2physiological races as a new pathogenic type both in Hubei and Yunnan province.This study classify 6 different physiological races from 8 different Brassica hosts strains,with the largest number of physiological races in chinese cabbage,and the number of oilseed rape was second.4.Identification results comparative analysis about "0,1" hosts system,"Threshold" hosts system and Williams hosts system.The "0,1" system is the same as the Williams system has the ability to identify 16 races.Among them,the 4 race is the most pathogenic to all differential hosts.Because of complex pathogen from the field collection for a virulent one will cover up the weak races,the Williams4 can be divided into 6 races as well as Williams 7 can be divided into 3 kinds of races by "0,1" system.The "threshold" system can divide Williams 4 into 3 races and divide "0,1" 4 into 2 races;but the "threshold" identification system has only the ability to identify 8races,in a smaller number than "0,1" identification system.Williams system and "threshold" systemis are both based on a DI amount to divide resistance and sense,but "0,1" system is based on the different on "quality" standard is clearer,the error is smaller,operating easily and the hosts are easy to obtained.Therefore the "0,1" identification system as the most suitable for our conditions P.brassicae physiological race identification system.