| Ditylenchus destructor is a phytopathogenic nematode with a high degree of harm.It is widely distributed in Europe,North America,Australia,Asia and Africa.It is classified as a quarantine pest in many countries.The devastating damage to the sweet potato production areas in North China,Northeast China,and East China has seriously hampered the development of the sweet potato industry.This root rot on Angelica sinensis caused by D.destructor is most important disease.In recent years,scholars have continued to find traces of D.destructor on potatoes.However,the major occurrence of D.destructor is mainly on sweet potato and Angelica sinensis.The D.destructor population has differences in parasitic and pathogenicity as well as in the ITS region of ribosomal RNA and D2-D3 region on 28 s.Different populations also show differences in morphological traits.However,most of the studies on D.destructor in China are the populations of D.destructor in the sweet potato production region.There are few studies on parasitic,pathogenicity and genetic differentiation of D.destructor from Angelica sinensis populations.In this Paper,the occurrence of D.destructor disease on A.sinensis was investigated in Dingxi city,nematode samples were observed under the optical microscope and rDNA-ITS sequencing of D.destructor populations from Chinese angelica,codonopsis and potato,were analyzed to determin intraspecific differentiation.The main findings are as follows:1.From October to November 2017,during the harvest period of Chiese angelica,the incidence of Angelica sinensis disease in 30 plots in 9 towns in Zhangxian county,Minxian county,and Weiyuan county were investigated through a five-point sampling method.The results of the survey showed that the most serious cases were found in the villages of Sishengdi,Zhang County,which had an incidence rate of 92.4% and a disease index of 87.25.The average incidence of other plots was as high as 62.52%,and the disease index was 40.81.2.Morphological identification and description of 9 nematode populations were carried out using light microscopy,and their main characteristics were compared with the reported populations.The results showed that these 9 groups belonged to Ditylenchus,but there were differences in morphometric values between the populations from different hosts andgeographic regions.The analysis of results showed that there were no discontinuities in the morphological characteristics among different populations of D.destructor species,there was no stable differentiation,and it was not possible to classify the physiological race based on morphological characteristics.3.Using molecular biology techniques,primers of F194 and F195 were used to carry out rDNA-ITS gene amplification and sequence analysis on 9 populations collected..The sequences obtained were compared by Blast and 16 sequences with high homology were downloaded.The sequences of two turfgrass nematodes(DQ5209321.1,AY703063.1)were taken as outgroups and nine populations of D.destructor in Gansu were included.The phylogenetic tree of the ITS region were constructed using the UPGMA method in MEGA6.The phylogenetic tree showed that the ZXC Codonopsis population in Zhangxian County was the same as the ZXA Angelica sinensis population inZhangxian County,and the homology of the A-type populations(EF210366,EF088935,and EF210372)reported in the sweet potato group was 100%.Population MXA-2 and population MXC were clustered together with F-type(DQ471335)from Astragalus membranaceus and F-type(HQ235677)on sweet potato.The HLS population and D-type(EF208213)are clustered together and have close genetic relationships.The HCA,MXA-1 population and C-type population have high affinity and are clustered together.The LXC and TCC groups are less closely related to each other and have the closest relationship with the reported groups.4.Nine low-toxicity agents were selected to test laboratory toxicity using direct-killing method.The results of agents effect on D.destructor showed that the poisoning effect of42%metam-sodium had a good killing effect on D.destructor,and the corrected mortality rate reached 97.05% after 72 hours.Followed by 5% Fosthiazate and 41.2% Velum poisoning effect is better,after 72 hours of action,the corrected mortality can reach 77.05%,61.93%,while the corrected mortality of other agents are below 30%,no obvious Poisoning effect.According to the virulence regression equation,correlation coefficient,LC50 and 95%confidence interval,it can be seen that at the same concentration,the virulence effect of the three agents is best 5% Fosthiazate,followed by 42% metam-sodium,However,41.2% of Velum was less effective... |
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