Study On Genetic Diversity,Virulence Differentiation And Cross Infection Of Verticillium Dahliae From Sunflower And Potato

Verticillium wilt is a typical soil-borne and seed dispersal disease caused by Verticillium dahliae.V.dahliae has a broad range of hosts and can infect potatoes and sunflowers resulting in yield loss and quality decreasing.In this study,we identified vegetative compatability groups,physiological race types,mating types,virulence differentiation and phylogenetic analyses based on IGS sequences of 58 strains isolated from different locations and hosts(29 isolated from potatos and 29 isolated from sunflowers).In the mean time,we performed cross infection of these 58 isolates on potatos and sunflowers.The results as followed:Standardstrains of different VCGs were used to divide the testing strains into different VCGs.The results showed that the 29 strains from potatos were divided into three VCGs,i.e.VCG2B(11 strains,37.9% of testing strains),VCG4B(2 strains,6.9%),and VCG4A(16,55.2%).Twenty nine strains from sunflowersstrains were identified as three VCGs as well,i.e.VCG2B(10 strainsa,34.5%),VCG4B(12 strains,41.4%)and VCG4A(7 strains,24.1%).Physiological race types of 58 strains were identified by using the universally specific primers..The results show that all 58 strains were Race2.Mating type identification of 58 strains were identified by using the universally specific primers..The results showed all 29 strains isolated from potato verticillium dahliae were MAT1-2-1.Twenty three out of 29 strains isolated from sunflowers were identified as MAT1-1-1 and 6 were identified as MAT1-2-1.The phylogenetic tree of 58 strains was constructed based on IGS sequences of V.dahliae and 58 strains were classified as four groups,i.e.group I,II,III and IV..Group I included all 29 strains isolated from potatoes planted in Inner Mongolia and the VCGs of this group were quite diverse.Group II contained 6 strains isolated from potato and 1 strain isolated from sunflower,Six potato V.dahliae were isolated from Xilin Gol,Heilongjiang,and the northeast of Jilin province.All 6 strains showed weak pathogenicity.The only one sunflower strain was isolated from Baicheng in Jilin province.Group III contained 21 sunflower strains isolated from Jilin,Liaoning,Shanxi,Hebei and Inner Mongolia.GroupIV contained 2 subgroups,one of them included 3 sunflower strains(2 isolated from Xinjiang and 1 isolated from Liaoning).And the other subgroup contained 4 sunflower strains isolated from Guyuan in Ningxia.One strain of Verticillium albo-atrum isolated from potato and 3 strains of V.dahliae isolated from tomato,cotton and lettuce were clustered as outgroups.To identify the pathogenicity of 58 V.dahliae strains,we performed the infection assays by root inoculation of conidia on their own hosts.The results showed that all of the strains were able to infect their own hosts.Among the 29 potato strains,the one named NCP-1(isolated from Pingdiquan Town,Chahar Youyiqian Banner,Inner Mongolia Autonomous Region)had the highest pathogenicity and the disease index was 83.33.The strains NWD-2(isolated from Shibaqing town,Shangdu County,Wulanchabu,Inner Mongolia)had the lowest pathogenicity and the disease index was only 10.85.Among the29 sunflower strains,the one named GYC4(isolated from Guyuan,Ningxia)had the highest pathogenicity and the disease index was 47.64.The strain GYC1(collected from Guyuan,Ningxia)had the lowestpathogenicity and the disease index was 13.42.AWe summarized the correlation between classification of VCGs and pathogenicity of 58 strains.It was found that the pathogenicity of different VCG types either from the same host or different hosts were distinct.Regarding to the results of potato strains,the pathogenicity of VCG4 B was the highest and the average disease index was 73.34.The pathogenicity of VCG2 B was the second highest and the average disease index was 37.77.The pathogenicity of VCG4 A was the lowest and the average disease index was20.53.Regarding to the results of sunflower strains,the pathogenicity of of VCG4 A was the highest and the average disease index was 42.64.The second highest one was VCG4 B and the average disease index was 31.46.The lowest one was VCG2 B and the average index was 18.47.The results of cross infection between potato and sunflower strains indicated that the potato strains showed higher pathogenicity on sunflowers than on potatoes.The sunflower strains showed higher pathogenicity on sunflowers that on potatoes.