The Pathogenicity Of Plasmodiophora Brassicae From Different Locations,the Ultramicroscopic Structure And Genetic Diversity Of Resting Spores

Clubroot disease is an important disease on cruciferous crops caused by Plasmodiophora brassicae.P.brassicae has pathogenicity differentiation.It has not been reported that if P.brassicae has variant type,specialization and if they have morphological differences.The purpose of this study is to explore the pathogenicity of P.brassicae from different locations to plants of different families and genera,ultrastructural structure and genetic diversity of resting spores.The following progress has been obtained through the study:1.The pathogenicity of P.brassicaeFirst we collect galls from ten different field locations of Sichuan,Hubei,Shaanxi Province then grind and centrifuge to get spore suspension,inoculate those 10 spore suspension to 8 kinds of non-cruciferae plants and 18 kinds of the cruciferous weeds(Most of them are the host plants of P.brassicae and have been reported)respectively.The results show that none of the non-cruciferous plants can get infected,the reason could be that there is pathotype differentiation,it also shows that P.brassicae has pathogenic differentiation in familiy.The second reason may be that the plants have various resistance to the pathogen,causing the failure of the infection.Different genera of the cruciferous plants such as Eruca,Capsella bursa-pastoris,Hesperis matronalis,Wasabia japonica,Sinapis,Malcolmia,Erysimum,Isatis,Arabidopsis thaliana can get the disease.Orgchophragmus,Lepidium sativum,Cheiranthus,Iberis are also from different genera of the Family Brassicacea,the aboved hosts react differently to the same spore suspension.Descuminiasophia,Lobularia maritime,Matthiola,Cheiranthus,Aubrieta cultorum did not get infected.2.Scanning electron microscope observations of resting sporesResting spores of P.brassicae from different places were observed under scanning electron microscopy(sem).Resting spores surface ornamentation is different between different regions,it can be divided into three categories.Class A spore surface has spiny protrusions,sharp projections,and a larger density including Zhijiang and Jiulong two regions;Class B spore surface ornamentation has block protrusions with a bigger density,including Xinduqiao,Lucheng,Anxian,Class C reticulate projection base connected into a network,the density of the protrusions is small,including Dayi,Taibai,Lixian,Guanghan,Shifang.The average diameter of spores was 2.975 to 3.291 μm.Inoculated with the same spore suspension,different genera of Cruciferae plants spore look the same.3.The genetic diversityWe selected 6 primers giving clear bands and with good polymorphism from all screened 30 ISSR primers.81 bands containing 79 polymorphism bands were obtained by PCR amplification with the 6 primers.The polymorphism proportion is 97.53%.Clustering tree was built by UPGAM method according to similarity coefficient between the 10 strains,range between 0.46 and 0.83,with a mean of 0.64.When the similarity coefficient was 0.66,all the strains can be divided into three groups.Group Ⅰ include Lucheng,Xinduqiao,Jiulong,Shifang,Dayi,Guanghan,Taibai,Lixian 8 strains.Group Ⅱ includes Anxian strain.Group Ⅲ includes Zhijiang strain.Based on the the SM,the strain of Anxian and Zhijiang may be distant genetically from other 8 strains.We selected 8 primer pairs giving clear bands and with good polymorphism from all screened 81 pair of SRAP primers.109 bands containing 106 polymorphism bands were obtained by PCR amplification with the 8 primers.The polymorphism proportion is 97.24%.Clustering tree was built by UPGAM method according to similarity coefficient between the 10 strains,range from 0.58 to 0.83,with a mean of 0.70.When the similarity coefficient is 0.60,all the strains can be divided into three groups.Group Ⅰ include Lucheng,Lixian,Jiulong,Shifang,Dayi,Xinduqiao,Guanghan,Taibai 8 strains.Group Ⅱincludes Anxian strain.Group Ⅲ includes Zhijiang strain,Based on the the SM,the strain of Anxian and Zhijiang may be distant genetically from other 8 strains.We used both ISSR and SRAP to explore the genetic relationship of P.brassicae between 10 different areas.Through the polymorphism analysis,calculate similarity coefficient.The resut of ISSR and SRAP were similar,both the two molecular techniques can divide 10 different regions of the DNA template into three groups and set the Anxian strain and Zhijiang strain into different groups.The similar coefficient of the two strains and other strains is small,the genetic relationship is distant.