| Radopholus similis(Cobb,1893)Thorne(1949)is a devastating plant migratory endoparasitic nematode,which seriously damages many tropical plants.It is listed as a plant quarantine pest by many countries.Lycopersicon esculentum and Nicotiana benthamiana are model plants for studying interactions between plants and pathogenic organisms or insects.At present,tomato and tobacco have been mainly used to study interaction between root knot nematode and its host,but there are few reports on R.similis.In order to use tomato and tobacco to study pathogenicity mechanism of R.similis,in this study,indoor quartz sand cultures at 25±1℃were used to carry out the parasitism and pathogenicity research of R.similis in tomato and tobacco,and optimized inoculation conditions were established.The specific research results are as follows.1)The results showed that R.similis infected tomato and tobacco roots.Symptoms occurred earlier in tobacco than in tomato(9 dpi vs 16 dpi).R.similis propagated in both the roots of tomato and tobacco,and eggs of R.similis were observed in the roots of tomato and tobacco after 23 days and 30 days post infection,respectively.In addition,the invading sites varied in the two plants,in tomato root,the main infection area was the cortex,and the epidermal cells were relatively complete;while in tobacco root,the infection areas were the cortex and epidermis.2)The optimum inoculum quantity and time for pathogenicity test of tomato and tobacco were determined.By comparing symptom variation in tomato and tobacco roots invaded by four populations under different inoculation amount and time,the optimized inoculation quantity of tomato infected by R.similis was 150 per plant,while tobacco was 150 or 200 per plant.Under the optimized inoculation quantity,the optimzied inoculation time of tomato and tobacco for detecting parasitic pathogenicity was 23 days.3)The results showed that pathogenicity of R.similis populations from different geographical and host origin was different.In the study of pathogenicity in tomato,SZ-SWK population is the most virulent while HN6 population is the weakest;in the study of tobacco,GJ-LY323 population is the most virulent while ML-HG population is the weakest.In addition,the pathogenicity of R.similis in tomato and tobacco was different.The infection of GZ-H,HL-XY,ML-HG,SZ-SWK and SZ-FZ populations was stronger in tomato than in tobacco,and tomato were more suitable to use as model host;as HN6 population as concerned,the infection was stronger in tobacco than in tomato,and tobacco were more suitable to use as model host;whilest,DBSR and GJ-LY323 populations have little differences in the infection of tomato and tobacco,and both can be used as model plants.In conclusion,in this study,by testing the process and regularity of the infection and pathogenicity of R.similis in tomato and tobacco,the parasitic pathogenicity characteristics of R.similis were clarified,and the optimized parasitism and pathogenicity inoculation system were: 30 days old seedlings were inoculating with 150 nematodes per plant or 200 nematodes per plant,reproduction rate,symptoms developing and plant growth were detected after 23 days post inoculation.In addition,the pathogenicity of eight populations of R.similis in the tested plants was determined,and the differences between different hosts and geographical sources R.similis were further clarified to be existed.It was further confirmed that the system of determining the pathogenicity of R.similis in tomato and tobacco as hosts was suitable for study of pathogenicity differences among different populations of R.similis,host range and host adaptability.The results also confirmed that different populations of R.similis have different adaptability to tomato and tobacco,and provided a reference tostudy host selection for nematode and host interaction,and is of great significance to further study the pathogenic mechanism and control methods of R.similis by using tomato and tobacco as model hosts. |
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