Study On Biocontrol Of Cucumber Root Rot Caused By Fusarium Solani With Trichoderma Viride-fermented Spent Mushroom Substrates

Cucumber root rot,caused by soil-borne Fusarium solani,is very ubiquitous in fields and greenhouses.Meanwhile,the occurrence and severity of the vegetable disease tend to be escalating terribly year by year,and this has significantly stymied the sustainable development of cucumber industry.Currently,the bioagent of Trichoderma sp.is the most promising arsenal to control the disease for its unique features such as long-lasting efficiency,inhibiting a wide spectrum of disease fungi and so on.In the study,one kind of nursery substrates,mainly comprised of spent mushroom substrates fermented with Trichoderma viride,was invented,and on the heel of that,the nursery substrates were utilised to control cucumber root rot.Relying on the technique of qPCR,the dynamics of Trichoderma viride and Fusarium solani,in the rhizosphere of cucumber seedlings,were consecutively detected.The results were following below.1.Trichodema viride Tr14 was screened out from the 26 strains of Trichoderma spp.maintained in the Department of Integrated Management of Vegetable Diseases,the Institute of Vegetables and Flowers of CAAS.The inhibitions of Trichodermav viride Tr14 against Fusarium oxysporum and Fusarium solani were 82.97%,95.73%,respectively.2.The technique utilized to produce secondary culture of Trichoderma-fermented spent mushroom substrates was optimized and determined,and the swift artificial propaganda method of Trichoderma-fermented spent mushroom substrates was established.The spore concentration of the substates of wheat bran and maize meal mixed at the mass proportion of 3:1,inoculated with 1×10⁸spores/g Trichoderma viride suspension at 20%dose,final water content adjusted to 60%,then maintained at 30?constant temperature conditions for 7 days,could reach 2.4×10¹⁰ spores/g.The prepared secondary culture was added to spent mushroom substrates at proportion of 1:100,which were weathered and then ground into pieces in advance,then water content adjusted to 60%.The spent mushroom substrates inoculated with secondary culture were maintained at 30?constant temperature for 15 days and then the spore concentration could reach 1×10⁹ spores/g.3.The optimized formula of nursery substrates were rolled out.The phisical and chemical properties of various substrates,made up of spent mushroom substrates?SMS?,vermiculite and peat at certain proportions,were determined,including pH,Ec,organic matter.The impacts of the mixed substrates on cucumber seedlings were assessed simultaneously.The mixed substrates performed much better than the control substrates?peat and vermiculite mixed at the proportion 7:3?in terms of porosity,conductivity,nitrogen,phosphorus and potassium contents,which tended to increase with increasing spent mushroom substrate levels.Among all the treatments,the T7?the proportion of SMS,peat and vermiculite was 1:1:1?performed best in terms of height,stem diameter,leaf area,chlorophyll content,the number of lateral roots,the overground and underground dry weights of the cucumber seedlings,which were 150%,175%,169%,114%,192%,191%,243%times respectively compared with control treatment.Therefore,spent mushroom substrates as the substitute of peat partly added in the nurturing media could facilitate the growth of cucumber seedlings auspiciously.4.The dynimics of Trichoderma viride and Fosurium solani in the rhizosphere were detected with the help of corresponding qPCR systems at different time intervals.5.The novel technique of site-fixed biological control against Cucumber root rot with Trichoderma viride-fermented spent mushroom substrates accompanied with non-woven bag was set up successfully.Trichoderma viride-fermented spent mushroom substrates,combined with non-woven bags,paper pots and paper tubes,could protect cucumber plants against soil-borne fungi diseases in an echo-friendly,efficient and pollution-free way.The inhibition of the site-fixed control technique could reach 88.35%,even higher than chemical fungicide.In the present study,the agriculture by-products and bioagent Trichoderma viride were utilized together to make seedling media,and this could not only solve the environment pollution problems posed by spent mushroom substrates,but also make full use of the spent mushroom substrates to replace peat partly so as to avoid the waste of resources.Simultaneously,the present study could be heuristic for us to explore a novel way to control vegetable diseases.