| Common root rot of wheat is a soil borne disease which widely spread in all parts of the world.In recent years,it has become a bigger threat to wheat production with increasing of the disease severity.In order to clarify the genetic diversity and pathogenicity differentiation of B.sorokiniana and the wheat resistance to the pathogen in Huanghuai Floodplain,the main area of wheat production of China,we collected the Samples in the field throughout Huanghuai wheat growing region in this study and the pathogens were identified through the tissue separation,morpholomorphology of isolates,and molecular technology.The genetic diversity of the pathogen was analyzed through the molecular markers of URP-PCR amplification.The inoculation assay of B.sorokiniana showed the variation of pathogenicity in the isolates which had relationship with geographic origin and genetic diversity.Meanwhile,we screened the resistance of 89 local wheat cultivars and 20 foreign germplasm materials to B.sorokiniana through the inoculation assay of the pathogen in pot and filed.The purpose of our researches aimed-to provide theoretical basis for monitoring and controlling of the wheat root rot,and breeding for the disease resistance.The main results were as follows:1.Samples displaying common root rot symptoms were collected from 55 places in 12 cities of Henan and Hebei provinces in 2014 and 120 places in 38 cities of Henan,Hebei,Anhui,Jiangsu,Shanxi,and Shandong provinces in 2015.A total of 74 and 188 strains of B.sorokiniana were isolated and identified by the morphology and molecular characteristics,respectively.The results showed that the frequency of all geographical populations in 2014 were more than 20%.The highest frequency of 40% was found in Middle and East Henan group and the lowest frequency of 21.43% was in Hebei group.The frequency in all geographical populations of Huanghuai floodplain were more than 30% in 2015 in which Henan group and Hebei group were more than 50% at range of 50.67 % and 61.02 %,respectively,while Shanxi group and Shandong group showed lower-frequency at 32.69 %and 31.65 %,respectively.Compared with that in 2014,the frequency of all geographical populations were higher in 2015.2.The genetic diversity of B.sorokiniana isolates in 2014 and 2015 were analyzed by the URP-molecular marker technology.On the basis of the optimization reaction conditions,5primers were screened out,which could produce the clear and stability and repeatability polymorphic bands.The date of amplification bands were analyzed by NTSYSpc2.10 e software.The results of the clustering and analysis showed B.sorokiniana in 2014 were divided into 6 groups in the similarity coefficient of 0.88 and-11 groups in 2015.The tested strains from different geographical groups was cross each other-which indicated that B.sorokiniana from Huanghuai wheat area was a complex population and existed obvious differentiation.The data of amplification bands were analyzed by popgene1.32 software.In2014,the mean of genetic diversity in the geographical populations(Hs),mean of geographical populations' genetic coefficient of differentiation(GST),and gene flow(Nm)was 0.1002,0.0867,and 5.2676,respectively.In the same way to analysis,-The value of Hs,GST,and Nm in 2015 was 0.1131,0.1601,and 0.26235,respectively.The similar results demonstrated the genetic diversity,and genetic variation among the populations in Huanghuai wheat area to be a certain extent,and frequent gene flow among the isolates of Huanghuai wheat area.Compared with the geographical source of the isolates and the genetic similarity,there existed a negative correlation relationship,i.e.the farther the geographical position,the lower the genetic similarity coefficient.3.The pathogenicity experiment of 74 isolates in 2014 and 46 isolates in 2015 were conducted in greenhouse on Aikang 58 wheat cultivars.Through significance test for disease index,the result showed that the pathogenicity of isolates had significant difference(P<0.001).Except Hebei group,the pathogenicity of isolates in all the group exhibited significant differentiation.To identify those with significant differences in geographic groups in 2014,the results from statistical significance analysis(p<0.01)demonstrated that the isolates had obvious differences in pathogenicity,whereas there was no significant differences among the five groups in pathogenicity,which the disease indexes were 62.16,59.85,58.37,57.61 and 57.62 for Hebei,South Henan,West Henan,North Henan,and Middle & East Henan,respectively(p>0.05).In the same way to analysis the data in 2015,the similar results of the significant difference in pathogenicity of the individual isolate(p<0.01)and no significant difference among the five groups were found,which the disease indexes were 42.10,44.47,41.83,40.98,44.51 and 61.43 for Henan,Hebei,Shanxi,Shandong,Anhui and Jiangsu group,respectively(p>0.05).The similar results in two years showed that there was no obvious correlations between pathogenicity and geographic origin.4.Through inoculation assay in pot along with the observation of disease symptom and species-specific primer pair detection of B.sorokiniana from wheat and corn tissues,the results showed that B.sorokiniana could not only infect wheat,but also the rot and stem base of corn.But B.sorokiniana couldn't expand extensively in the base of corn stalk to produce obvious typical disease symptoms.5.The resistance screening of 89 local wheat cultivars and 21 foreign germplasm materials were carried out in pots and field by inoculation of B.sorokiniana LK030093 isolate.The results showed that there was no immune or high level of resistance cultivars to common root rot among all the test materials even there was a little bit difference of resistance found.In the potted seedlings inoculation in greenhouse,there were 1,2,33 and 53 wheat cultivars with resistance,moderate resistance,susceptibility and high susceptibility in 89 local wheat cultivars,accounted for 1.12%?2.25%?37.08% and 59.55%,respectively;There were 1,5and 15 foreign germplasm materials with moderate resistance,suceptibility and high susceptible susceptibility in 21 foreign germplasm materials,accounted for 4.76%?23.81%and 70.14%,respectively.In the adult-plant stage(dough stage),resistance identification in the inoculated field,there were 2,20,35 and 33 wheat cultivars with resistance,moderate resistance,susceptibility and high susceptiblity in 89 local wheat cultivars,accounted for2.25% ? 22.47% ? 39.33% and 37.08%,respectively;there were 1,8,6 and 6 foreign germplasm materials with resistance,moderate resistance,susceptibility and high susceptibility in 21 foreign germplasm materials accounted for 4.76%?38.10%?28.57% and28.57%,respectively. |
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