Study On The Inhibitory Effect Of Strong Reducing Soil Treatment On Root-knot Nematodes

Root-knot nematode is a highly specialized type of plant-parasitic nematode,which has the characteristics of wide distribution,great variety of host species,and strong parasitism.In recent years,the facility agriculture is developing rapidly in China.However,due to the high-intensity planting mode and unreasonable nutrient management,the root-kont nematode disease has intensified year by year and has become a key barrier restricting the sustainable development of facility agriculture in China.Reductive soil disinfestation(RSD)is a method for quickly repairing degraded soil in facilities,which can effectively suppress soil-borne pathogens,but the effect and mechanism of action on root-knot nematodes are still unclear.Therefore,it is important to study the inhibitory effect and mechanism of RSD treatment on root-knot nematodes,as well as the changing patterns of soil nematode communities,especially herbivorous nematodes,driven by the host crop cultivation after RSD treatment.The results of this study will enrich the strategy for control of root-knot nematode disease and provide certain theoretical guidance and application value for achieving the green sustainable development of facility agriculture.In this study,the soil with high incidence of root-knot disease is researched based on the technical method of RSD treatment,using shallow dish method,sucrose centrifugation method and nematode morphology identification,etc.The following research content is included:(1)to study the inhibitory effect of RSD treatment on rootknot nematode and the influence on the structure of nematode communities through soil incubation experiment;(2)to study the inhibitory effect of organic acids that generated during RSD treatment on root-knot nematode through plate experiment;(3)to study the effect of tomato planting on soil nematode community,especially the plantparasitic nematodes after RSD treatment through pot experiment.The major findings are as follows: Soil incubation experiment indicates that RSD treatment can effectively kill soil root-knot nematodes with the killing rate reaching 88.7-94.6%,which is significantly higher than the thiazoline of 42.1%.Meanwhile,RSD treatment can also considerably change the composition of nematode trophic groups,with the relative abundance of bacterivores increased significantly,being 66.2-88.1%.Additionally,RSD treatment remarkably increases the maturity index of free-living nematodes,nematode channel ratio and Wasilewska index,but declines the plantparasitic index.Thus,RSD treatment is an agricultural practice that has the potential to rapidly remediate the root-kont nematode diseased soils.The result of the plate experiment shows that formic acid,acetic acid,propionic acid,and butyric acid can all effectively inhibit the activity of root-knot nematode second-stage juveniles(J2)and the hatching of oocysts,with the inhibitory effect varying with the type and concentration of organic acids.The inhibitory effect is gradually increased with the increment of organic acid concentrations.At the same time,different type of organic acids has various inhibitory effects on J2 activity and oocyst hatching.For example,0.5 m M formic acid and propionic acid inhibits J2 by more than 81.1%,which is more effective than the other two organic acids.The propionic acid has the strongest inhitbitory effect on oocyst hatching than the other three organic acids,with 0.5 m M propionic acid suppressing 88.1%.The result of pot experiment indicates that RSD treatment can not only suppress root-knot nematode,but also reduce the number of other plant-parasitic nematodes.Although the number of plant-parasitic nematodes gradually increases during the growth of host tomato,it is still significantly lower than that of control and thiazoline treatment.The number of plant-parasitic nematodes in the RSD treatment is only 2.2%-3.2% of the control group and 2.7%-4.1% of that with thiazoline treatment at the tomato flowering stage,indicating that the inhibitory effect of RSD treatment on plant-parasitic nematodes can maintain one crop season at least.In addition,the biomass of tomato plants in the RSD treatment is significantly higher than that of control group and that with thiazoline treatment.In conclusion,the results highlight the robustness of the effects of RSD on reducing the number of root-knot nematodes and other plant-parasitic nematodes in the soil,in which the organic acids generated during RSD process is a type of effective nematicidal substance.After RSD treatment,host crop cultivation could promote the recovery of plant-parasitic nematodes,but the level is still significantly lower than the threshold of diseased one.Therefore,the results of this study show that RSD treatment can effectively remediate the facility soils with high incidence of nematode diseases,which is of great significance for ensuring the sustainable development of highefficiency agriculture in China.