Study On Lotus Soil Microbial Diversity And Fusarium Wilt Disease Control Technology

Lotus rhizome rot disease, a soil-borne disease caused by Fusarium. oxysporum f. sp.nelumbicola, has been seriously restrict the development of lotus production. Currently, the research of F. oxysporum are carried out more in the world, but mainly focus on pathogenic mechanism and control of tomato blight, banana fusarium wilt and cotton fusarium wilt.However, there are still a few people studying lotus rhizome rot disease. The study has provided scientific background for the continuous cropping obstacle of this disease and for the pathogenic mechanism and control of the disease.Our study contents were mainly arranged as follows:1. Microbial diversity of lotus soil. Different continuous cropping lotus rhizosphere microorganisms were separated based on the traditional soil dilution method. All isolates were identified by 16 S rDNA gene sequences. We analyzed microbial compositions,abundance and diversity of soil samples from healthy or Fusarium wilt infected lotus fields with different years of continuous cropping by 16 S rDNA gene-based pyrosequencing and DGGE. Diversity index of the bacterial community in healthy soil increased with monoculture years, but decreased in Fusarium wilt infected soil, whereas the diversity of bacterial community in soil was relatively stable. Compared with healthy soil, the abundance of beneficial bacteria in Fusarium wilt infected soil significantly decreased over time. Altogether, soil weakness and lotus Fusarium wilt disease could be attributed to the changes of the soil microbial community and structure after long-term continuous cropping.Those changes include the reduction of beneficial microorganisms and the accumulation of fungal pathogens.2. Screening and identification of the biocontrol bacterium. Soil dilution method was used to screen bacterias antagonised to lotus rhizome rot disease from the field soil infected by F. oxysporum f. sp. nelumbicola. The results showed that YJa1, YJa2 and YJa4 strains of bacterias had obvious inhibition effects on F. oxysporum f. sp. nelumbicola.Culturing in PSB medium for 48 hours under 32? and pH7.0, the strain of YJa2 bacteria could promote the resistant to lotus rhizome rot disease3. Fungicides screening in laboratory. At this experiment, the effects of 9 fungicides against the F. oxysporum f. sp. nelumbicola were studied by the use of mycelial growth rate method. The results showed that 7 fungicides including epoxiconazole, diniconazole,carbendazol, tebuconazole, difenoconazole, hexaconazole, flutriafol strong inhibition effect on Fusarium oxysporum f. sp. nelumbicola, and their 50% effective concentration(EC50)value are 0.1023 ?g/mL, 0.1129 ?g/mL, 0.1284 ?g/mL, 0.5089 ?g/mL, 0.5609 ?g/mL,1.0583 ?g/mL and 0.2797 ?g/mL. While the toxicity of hymexazol was weaker than the above-mentioned seven, the EC50 value was 81.40 ?g/mL. Flutriafol embraced is the weakest toxicity in our research, the EC50 value of it was 1220.97 ?g/mL.