Effects Of Soil Fumigation Combined With Bio-Organic Fertilizer Application On Banana Fusarium Wilt Disease Suppression

The banana production industry was severely hampered by Fusarium wilt disease recent years.Soil fumigation shows effects on killing soil pathogens,but it also shows non-selective effects on killing all soil microorganisms.It has been widely reported that bio-organic fertilizer(BIO)can promote plant growth mainly through increasing soil fertility and regulating soil microflora.In order to investigate the effects of BIO on soil microbial community after fumigation,an experiment was conducted to explore the effects of soil fumigants on the suppression of banana Fusarium wilt disease in banana orchards,which has been monocultured with banana for 12 years and abandoned by farmers,and the effects of BIO application on fumigated soil microbial community using traditional plate-counting method,polymerase chain reaction denaturing gradient gel electrophoresis(PCR-DGGE)and Miseq prosequncing method.1.Effects of different fumigants on Fusarium suppressing and optimal fumigants screeningIn order to screen optimal fumigants for ensuring banana sustainable cultivation in banana monocultured planting orchards,effects of different soil fumigants,including lime,ammonium bicarbonate,the mixture of lime and ammonium bicarbonate,chlorine dioxide,sodium hypochlorite,hydrogen peroxide and ammonia water,on the number of Fusarium oxysporum f.sp.cubense race 4(FOC)in the soil was studied.Results demonstrated that all selected fumigants in current research showed the ability of suppressing soil FOC,however,ammonia water and the mixture of lime and ammonium bicarbonate showed more effective antifungal effect than other fumigants.Thus,these two kinds of fumigants were selected for further study.Pot experiments of different dosages of ammonia water and the mixture of lime and ammonium bicarbonate showed that a better antifungal effect was found when the soil fumigated with higher dosage.Both of the number and diversity of culturable bacteria and fungi decreased after the two kinds of fumigants applied,and the decline for bacteria is significantly lower than the fungi.Moreover,compared with the control,the indices of richness,evenness,stability and diversity of soil bacteria decreased gradually after soil fumigated with increasing dosage of fumigants.Furthermore,among the fumigated treatments,soil treated with ammonia water(2.67 ml·kg-1 soil)or a lime and ammonium bicarbonate mixture(3.33 g·kg-1 soil and 1.67 g·kg-1 soil,respectively)showed the highest microbial community indices.In conclusion,both ammonia water at the optimal application level of 2.67 ml·kg-1 and the mixture of lime and ammonia bicarbonate at the optimal application level of 3.33 g·kg-1 and 1.67 g·kg-1 can be used as good alternative soil fumigants.2.Effects of fumigants combined with bio-organic fertilizer application on banana Fusarium wilt disease suppressionA pot and field trial was set to investigate the effects of fumigants combined with bio-organic fertilizer(BIO)or cattle manure compost fertilizer(CM)application on banana Fusarium wilt disease,soil culturable microbes amounts and physiochemical properties.Results showed that the BIO application after fumigation controlled banana Fusarium wilt disease incidence effectively,improved banana plant biomass,and increased part of soil microbes amounts which decreased after fumigation simultaneously.Moreover,compared to non-fumigated control(CKCM,CKBIO),soil fumigated treatments(ACM,ABIO)controlled banana Fusarium wilt disease effectively,improved banana plant biomass,and increased soil fertility.In addition,the bio-organic fertilizer application combined soil ammonia water fumigation followed by the mixture of lime and ammonium bicarbonate fumigation was the best alternative methods for banana sustainable production.3.Effect of fumigants combined with bio-organic fertilizer application on soil microfloraTo study the effects of different fumigants combined with BIO on soil microflora,an experiment was performed to study the shifts of soil microbial community during fumigation and the recovery after BIO fertilizer application.Miseq sequencing analysis results showed that fumigation application decreased the relative abundance of Fusarium genus,improved soil physiochemical perproties,and manipulated soil microbial community probably through increasing the relative abundance of some beneficial bacteria and decreasing the relative abundance of pathogen.However,an important question remains after soil fumigation is that soil fumigation decreased the diversity of microbial community and broke the microbial community balance.Our further results showed that the fumigated soil micorflora can be recovered after BIO application by manipulating the structure of soil microbial community.Therefore,soil fumigation combined with BIO application not only controlled the spread of pathogen but also reconstructed the soil microflora.Based on all above results,soil fumigated with ammonia water at its optimal amounts changed the destructive microflora in abandoned banana orchard soil,thus controlled banana Fusarium wilt disease.Moreover,the BIO application after soil fumigation not only decreased Fusarium wilt disease incidence,but also rebuilt the soil microflora balance system probably by manipulating soil microbial community.In conclusion,the ammonia water combined with BIO application is a good alternative method for controlling banana Fusarium wilt disease.