| With the continuous increase of compound cropping index of greenhouse vegetables in China,the disease caused by root-knot nematodes became more and more serious year by year,and it became an important destructive disease in the production of greenhouse vegetables.Due to the serious harm of chemical control to the environment and human health,environmental protection and safety biological control technology has become a new research hotspot in recent years.Our previous study found that the addition of earthworms can significantly reduce the occurrence of cucumber root-knot nematode disease,but the relevant mechanism is still unclear.In this study,the cucumber continuous cropping soil was used as the research object.Firstly,the toxicity test was carried out to analyze the inhibition effect of different concentrations of earthworms and earthworm manure fermentation liquid on root-knot nematodes,and the composition of the fermentation liquid was analyzed by GC-MS.Furthermore,the optimum concentration of fermentation broth which could promote cucumber growth and inhibit root-knot nematode disease was selected through pot experiment.Finally,field experiments were conducted to determine the control effect of earthworm composting and biochar on root-knot nematode disease of cucumber in the facility,and the effects of earthworm composting on soil microbial flora were analyzed by high-throughput sequencing technology.The main conclusions are as follows:(1)Through indoor virulence identification,when the concentration of earthworm fermentation liquid was 10%,the relative inhibition rate of oocysts hatching was 73.58%,the hatching rate of in vitro eggs was 20.79%,and the mortality rate of second instar larvae was 82.22%.Both earthworm and vermicomectic fermentation could significantly inhibit root-knot nematode egg hatching and the survival of the second instar larvae,and the inhibition effect of earthworm fermentation was better than that of earthworm manure.GC-MS analysis showed that 151 and 148 compounds could be detected in earthworm and vermicompost fermentation broth,respectively,and their components and contents were different.Among them,phenylacetaldehyde,palmitic acid,benzene compounds and naphthalene had nematoidal effects.(2)The effects of different concentrations of earthworms and vermicompost fermentation on cucumber growth and root-knot nematodes control were measured through pot experiment,and soil nutrients and enzyme activities were measured.The results showed that 10%earthworm fermentation broth could reduce the occurrence of root-knot nematode disease by 66.8%compared with no watering(CK).In addition,both earthworm and vermicompost fermentation broth showed a trend of promoting cucumber growth at low speed and inhibiting it at high speed.Compared with CK,7.5%earthworm fermentation broth increased plant height,stem diameter and chlorophyll,respectively,and(p<0.05).Compared with CK,the activities of available nitrogen,available potassium,organic matter and phosphatase increased by 77.16%,41.29%,33.53%and 63.84%,respectively(P<0.05),can improve soil fertility.(3)Effects of different soil treatments on the number of cucumber root-knot nematodes showed that earthworm in situ+biochar treatment had a significant control effect on the number of cucumber rootknot nematodes in the whole period,in which the pest decline rate was 66.51%and 80.42%,the plant incidence was only 13.33%and the control effect was 78.57%in full fruit stage and seedling stage,respectively.In addition,the control effect of earthworm in situ composting and biochar on root-knot nematodes was 71.42%and-3 5.71%,respectively.(4)The results of high-throughput sequencing showed that the Ace index,Simpson index and Shannon index of continuous cropping cucumber rhizosphere bacteria under VB were significantly higher than those under CK,which were 44.84%,45.63%and 15.1%higher,respectively(P<0.05).For rhizosphere fungi in cucumber continuous cropping soil,the richness and diversity of soil fungal community were also increased by each treatment compared with the control.The correlation analysis between the number of cucumber root nodules and soil microbial flora showed that the number of cucumber root nodules was significantly positively correlated with Proteobacteria,Acidobacteriota and Basidiomycota.There was a significant negative correlation between the number of root nodules of cucumber and Actinobacteriota,Patescibacteria and Rozellomycota. |
